It is also reasonably cheap, unreactive and easy to purify.
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Apple's stock was unreactive today, as is typically the case with hardware spectacles like these.
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" After all, as the tank's description reads: "Let the boys know that your vagine is just as precious and unreactive.
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The two descriptions go hand in hand, actually, as in this case "noble" is from a German word for unreactive.
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"The annihilator forms a complex with one molecule from one competitor and one molecule from a different competitor and reacts to form inert, unreactive species," Cherry said.
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Dr. Beecher's committee, in a report titled "A Definition of Irreversible Coma," defined a new state of death — brain death — in which patients were unconscious, unresponsive to pain and unable to breathe on their own, and had no basic reflexes (pupils unreactive to light, no gag reflex and so on).
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Most organohalides will work, but carbon-fluorine bonds are generally unreactive, except with specially activated magnesium (through Rieke metals).
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Clamp connections are absent. Several chemical tests can be used to help verify an identification of L. rugosiceps. A drop of ammonium hydroxide solution turns the cap cuticle a reddish color or is unreactive, and yellow or unreactive on the flesh. A drop of dilute potassium hydroxide (KOH) turns the cap surface red, and the flesh yellowish to orangish.
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Solutions of NaClO4 are often used as an unreactive electrolyte. It is used in standard DNA extraction and hybridization reactions in molecular biology.
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Boc-protected amines are unreactive to most bases and nucleophiles, allowing for the use of the fluorenylmethyloxycarbonyl group (Fmoc) as an orthogonal protecting group.
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The density of gold is higher than most other metals, making it difficult to pass counterfeits. Additionally, gold is extremely unreactive, hence it does not tarnish or corrode over time.
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Both pyrimidines and purines resemble pyridine and are thus weak bases and relatively unreactive towards electrophilic aromatic substitution.Carey, Francis A. (2009). Organic Chemistry, ed. 6, Mc Graw Hill. p. 1206. .
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The cations obtained by reaction of methane with + HF are stabilized by interactions with the HF molecules. At low pressures (around 1 mmHg) and ambient temperatures, methanium is unreactive towards neutral methane.
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The reactivity of a methyl group depends on the adjacent substituents. Methyl groups can be quite unreactive. For example, in organic compounds, the methyl group resists attack by even the strongest acids.
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Wiberg 2001, p. 824 It is a relatively unreactive element. According to Rochow,Rochow 1973, p. 1337‒38 the massive crystalline form (especially if pure) is "remarkably inert to all acids, including hydrofluoric".
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The crystallized product was found to be stable under inert atmosphere and unreactive towards hydrogen gas, carbon dioxide, and ammonia. Furthermore, they were found to melt at 195 °C and decompose at 220 °C.
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Another approach is through direct insertion of carbenes onto the polyolefin backbone. Though post-functionalization techniques are viable for the insertion of functional groups, harsh conditions must be used since regular non-functionalized polyolefins are highly unreactive.
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Kr(H2)4 and H2 solids formed in a diamond anvil cell. Structure of Kr(H2)4. Krypton octahedra (green) are surrounded by randomly oriented hydrogen molecules. Like the other noble gases, krypton is chemically highly unreactive.
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193 It is mostly unreactive at room temperature but is slowly attacked by hot concentrated sulfuric or nitric acid.Greenwood & Earnshaw 2002, p. 373 Germanium also reacts with molten caustic soda to yield sodium germanate Na2GeO3 and hydrogen gas.
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Ramsay's remaining five unreactive substances were called the inert gases (now noble gases). Although Mendeleev's table predicted several undiscovered elements, it did not predict the existence of such inert gases, and Mendeleev originally rejected those findings as well.
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Zirconia is chemically unreactive. It is slowly attacked by concentrated hydrofluoric acid and sulfuric acid. When heated with carbon, it converts to zirconium carbide. When heated with carbon in the presence of chlorine, it converts to zirconium tetrachloride.
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Contrary to some earlier reports, ethenium was found to be largely unreactive towards neutral methane at ambient temperature and low pressure (on the order of 1 mmHg), even though the reaction yielding sec- and is believed to be exothermic.
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The spores are cylindrical, hyaline, and smooth, measuring 8–11 by 2.5–3.5 µm. They are unreactive in Melzer's reagent. Oligoporus fragilis is similar in appearance, but can be distinguished microscopically from Amylocystis lapponica by the lack of amyloid cystidia.
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Although rather unreactive, cyclohexane undergoes catalytic oxidation to produce cyclohexanone and cyclohexanol. The cyclohexanone-cyclohexanol mixture, called "KA oil", is a raw material for adipic acid and caprolactam, precursors to nylon. Several million kilograms of cyclohexanone and cyclohexanol are produced annually.
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The pool of unreactive catalytic complexes, as described in the reservoir effect, can be the result of several factors. One of these could potentially be an aggregation effect amongst the heterochiral catalytic complexes that takes place prior to the steady state equilibrium.
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SPhos is a phosphine ligand derived from biphenyl. Its palladium complexes exhibit high activity for Suzuki coupling reactions involving aryl chlorides, which are unreactive with palladium complexes of most other phosphine ligands. The ligand has convenient handling characteristics since it is air-stable.
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The release of OPC-specific antibodies by chronically demyelinated axons have been implicated as a remyelination inhibitor. Other proposed mechanisms posit that OPC migration is inhibited by either molecules expressed by chronically demyelinated axons or the accumulation of unreactive astrocytes in MS lesions.
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The reaction attracted much attention because hydrocarbons are normally unreactive substrates, whereas some sigma-bond metatheses are facile. Unfortunately the reaction does not readily allow the introduction of functional groups. It has been suggested that dehydrocoupling reactions proceed via sigma-bond metathesis.
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For many applications, the counterion simply provides charge and lipophilicity that allows manipulation of its partner ion. The counterion is expected to be chemically inert. For counteranions, inertness is expressed in terms of low Lewis basicity. The counterions are ideally rugged and unreactive.
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They are smooth and thin-walled, hyaline (translucent), with an allantoid (long with rounded ends) to broadly ellipsoid shape. They are unreactive with Melzer's reagent. The basidia (spore-bearing cells) are thin walled and club shaped, measuring 6–10 by 3–4 µm.
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PCBs are fairly chemically unreactive, this property being attractive for its application as an inert material. They resist oxidation. Many chemical compounds are available to destroy or reduce the PCBs. Commonly, PCBs are degraded by basis mixtures of glycols, which displace some or all chloride.
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Generally, amino acid residues are unreactive toward nucleophiles, but the dehydroamino acids are exceptions to this pattern. For example, dehydroalanine adds cysteine and lysine to form covalent crosslinks.Dawid Siodłak "α,β-Dehydroamino Acids in Naturally Occurring Peptides" Amino Acids 2015, vol. 47, pp. 1–17. .
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Tile alkyl group R should be primary or methyl, and preferably should be allylic or benzylic. Secondary halides react poorly, and tertiary halides don't react at all because a competing E2 elimination of HX occurs instead. Vinylic and aryl halides are also unreactive because backside approach is sterically prevented.
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For potassium, higher concentrations were found throughout the reactive pulvini, while a high concentration difference in the top and bottom halves of the unreactive pulvini was found. Upon stimulation to the reactive pulvini, an average of a 240% increase in potassium was found in the pulvini cells. Analysis of chloride ions gave similar results where high concentrations were found throughout the reactive pulvini, except in the unreactive pulvini the difference in concentration in the top and bottom pulvini was not significant. Overall, what was found was that high concentrations of potassium, chloride, and calcium led to a rapid decrease in water in the pulvini, which results in the drooping of the M. pudica leaves.
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Thus the ability of these heterobenzenes to undergo the Diels Alder reaction with this electrophile increases down the periodic table. Bismabenzene is so reactive that it exists in equilibrium with its dimer. Arsabenzene is far less basic than pyridine, being unreactive with Lewis acids. Trifluoroacetic acid does not protonate the molecule.
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Hexane () is a straight-chain alkane with six carbon atoms and has the molecular formula C6H14. Hexane is a significant constituent of gasoline. It is a colorless liquid, odorless when pure, and with boiling points approximately . It is widely used as a cheap, relatively safe, largely unreactive, and easily evaporated non-polar solvent.
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Phaeotrametes decipiens has brownish, fan-shaped fruit bodies. It has a trimitic hyphal system–containing generative, skeletal, and binding hyphae. Its spores are large, truncate, and thick-walled, and inamyloid (unreactive with Melzer's reagent). A characteristic feature of Phaeotrametes is the presence of chlamydosporic fruit bodies that occur alongside the normal fruit bodies.
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Wishart called the tumour fungus haematodes. From the features he describes (child with watery inflamed eye, unreactive pupil, cloudy white exudate in posterior chamber and lesion arising from the retina), it has been interpreted as representing a retinoblastoma, for which enucleation was, and remained the only treatment offering the prospect of a cure.
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Quaternary ammonium cations are unreactive toward even strong electrophiles, oxidants, and acids. They also are stable toward most nucleophiles. The latter is indicated by the stability of the hydroxide salts such as tetramethylammonium hydroxide and tetrabutylammonium hydroxide. Because of their resilience, many unusual anions have been isolated as the quaternary ammonium salts.
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The use of oxamide in concentrations of 1-3 wt% has shown to slow the linear burn rate while having minimal impact on propellant specific impulse. N, N'-substituted oxamides are supporting ligands for the copper-catalyzed amination and amidation of aryl halides in (Ullmann-Goldberg reaction), including relatively unreactive aryl chloride substrates.
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Exchange rates usually follow the trend I > Br > Cl. Alkyl- and arylfluoride are generally unreactive toward organolithium reagents. Lithium halogen exchange is kinetically controlled, and the rate of exchange is primarily influenced by the stabilities of the carbanion intermediates (sp > sp2 > sp3) of the organolithium reagents.The Preparation of Organolithium Reagents and Intermediates Leroux.F., Schlosser.
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Bis(triphenylphosphine)iminium chloride is the chemical compound with the formula [(C6H5)3P)2N]Cl, often written [(Ph3P)2N]Cl and abbreviated [PPN]Cl or [PNP]Cl. This colorless salt is a source of the PPN+ cation, which is used as an unreactive and weakly coordinating cation to isolate reactive anions. PPN+ is a phosphazene.
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The buffer should also be unreactive and not modify or react with most proteins. Different buffers may be used as cathode and anode buffers, respectively, depending on the application. Multiple pH values may be used within a single gel, for example in DISC electrophoresis. Common buffers in PAGE include Tris, Bis-Tris, or imidazole.
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They are of importance to speleologists because they have formed in sandstone. Large cave systems are not often found in this type of chemically unreactive rock. Kalk Bay is also home to the tiny but locally famous surf spot named "Kalk Bay Reef". This is renowned for heavy barrels and the associated shallow reef.
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H2 is relatively unreactive. The thermodynamic basis of this low reactivity is the very strong H-H bond, with a bond dissociation energy of 435.7 kJ/mol. The kinetic basis of the low reactivity is the nonpolar nature of H2 and its weak polarizability. It spontaneously reacts with chlorine and fluorine to form hydrogen chloride and hydrogen fluoride, respectively.
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Despite being in low formal oxidation states, metal carbonyls are relatively unreactive toward many electrophiles. For example, they resist attack by alkylating agents, mild acids, and mild oxidizing agents. Most metal carbonyls do undergo halogenation. Iron pentacarbonyl, for example, forms ferrous carbonyl halides: :Fe(CO)5 \+ X2 → Fe(CO)4X2 \+ CO Metal–metal bonds are cleaved by halogens.
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Icosane's size, state or chemical inactivity does not exclude it from the traits its smaller alkane counterparts have. It is a colorless, non-polar molecule, nearly unreactive except when it burns. It is less dense than and insoluble in water. Its non- polar trait means it can only perform weak intermolecular bonding (hydrophobic/van der Waals forces).
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Structure of the polymeric diethyl ether peroxide The C-O bonds that comprise simple ethers are strong. They are unreactive toward all but the strongest bases. Although generally of low chemical reactivity, they are more reactive than alkanes. Specialized ethers such as epoxides, ketals, and acetals are unrepresentative classes of ethers and are discussed in separate articles.
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Historic benzene formulae as proposed by August Kekulé in 1865. The ouroboros, Kekulé's inspiration for the structure of benzene. In the 19th century chemists found it puzzling that benzene could be so unreactive toward addition reactions, given its presumed high degree of unsaturation. The cyclohexatriene structure for benzene was first proposed by August Kekulé in 1865.
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The structure of active centers in Ziegler–Natta catalysts is well established only for metallocene catalysts. An idealized and simplified metallocene complex Cp2ZrCl2 represents a typical precatalyst. It is unreactive toward alkenes. The dihalide reacts with MAO and is transformed into a metallocenium ion Cp2Zr+CH3, which is ion-paired to some derivative(s) of MAO.
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Fluoroelastomers, like other elastomers (artificial rubbers), consist of disordered polymer chains connected in three dimensions. The main challenges in making fluorelastomers are cross-linking (reacting the unreactive polymers), as well as removing the HF formed during curing. There are three main families of fluoroelasters. VDF/HFP is a copolymer system of vinylidene fluoride and (at least 20%) hexafluoropropylene.
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Its ability to cleave DNA is greatly increased in the presence of NADPH and thiol compounds. This compound has also found prominence as an antitumor agent. 200px Chromoprotein enediynes are characterized by an unstable chromophore enediyne bound to an apoprotein. DNA cleavage caused by the C-1027 chromoprotein The chromophore is unreactive when bound to the apoprotein.
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In the laboratory, and usually for illustrative purposes only, ethyl esters are typically hydrolyzed in a two- step process starting with a stoichiometric amount of a strong base, such as sodium hydroxide. This reaction gives ethanol and sodium acetate, which is unreactive toward ethanol: : Under anhydrous conditions, strong bases induce the Claisen condensation to give ethyl acetoacetate: :Preparation of ethyl acetoacetate.
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The term inert may also be applied in a relative sense. For example, molecular nitrogen is an inert gas under ordinary conditions, existing as diatomic molecules, . The presence of a strong triple covalent bond in the molecule renders it unreactive under normal circumstances. Nevertheless, nitrogen gas does react with the alkali metal lithium to form compound lithium nitride (Li3N), even under ordinary conditions.
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Cryptobacterium curtum is asaccharolytic and unreactive in many of the conventional biochemical tests. Instead, it is able to degrade arginine and other amino acids found in oral cavities by using the arginine deiminase pathway. This bacterium is able to degrade arginine and produce substantial amounts of citrulline, ornithine and ammonia. Arginine and citrulline support the growth and reproduction of C. curtum.
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The end product cannot not be made in a single DA step because equivalent dienophile is either unreactive or inaccessible. An example of such approach is the use of α-chloroacrylonitrile (CH2=CClCN). When reacted with a diene, this dienophile will introduce α-chloronitrile functionality onto the product molecule. This is a "masked functionality" which can be then hydrolyzed to form a ketone.
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Although required for life, nitrogen is stored in the biosphere in an unreactive ("unfixed") form N2, which supports only a few life forms. Reactive nitrogen is however "fixed" and is readily converted into protein, which supports life, leading to depletion of oxygen in fresh waters by eutrophication. Nr is removed from the biosphere via Denitrification. A schematic representing the marine nitrogen cycle.
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Many groups have reported dehalogenation processes using different forms of homogeneous and heterogeneous transition metal complexes such as 0M, metal-ligand complexes, metal salts, and metal supported on different supports.Grushin, V.; Alper, H. Activation of otherwise unreactive C-Cl bonds. Top. Organomet. Chem. 1999, 3, 193-226. Vanadium compounds in its low oxidation state tends to perform dehalogenation reaction via one electron reduction.
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Xenon is a chemical element with the symbol Xe and atomic number 54. A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts. Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized.—National Standard Reference Data Service of the USSR.
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The energy released in the reaction of sodium and elemental sulfur is the basis of battery technology. The sodium–sulfur battery and the lithium–sulfur battery require high temperatures to maintain liquid polysulfide and Na+-conductive membranes that are unreactive toward sodium, sulfur, and sodium sulfide. The compound (C5H5)2TiS5 is an example of a polysulfide complex. Polysulfides are ligands in coordination chemistry.
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Xenon is a chemical element with the symbol Xe and atomic number 54\. It is a colorless, dense, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized.—National Standard Reference Data Service of the USSR.
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Marker's research at Pennsylvania State College (now Pennsylvania State University) was directed towards finding synthetic routes to steroid hormones from "relatively inexpensive starting materials".. While working on a series of plant steroids called sapogenins, he realized that the structure of the side chainSteroids are characterized by four fused rings of carbon atoms (three six-membered rings and one five-membered ring). Many steroids also have a "side chain" of carbon atoms, usually attached to the five-membered ring. of one of the compounds, sarsasapogenin, had been incorrectly described in the literature: rather than having an unreactive "double-tetrahydrofuran" side chain, it actually had a much more reactive "ketone spiro acetal" side chain. While the ketone spiro acetal was unreactive in basic or neutral conditions, it could be degraded under acidic conditions: indeed, Marker described it as "unusually reactive".
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Metastable and kinetically persistent species or systems are not considered truly stable in chemistry. Therefore, the term chemically stable should not be used by chemists as a synonym of unreactive because it confuses thermodynamic and kinetic concepts. On the other hand, highly chemically unstable species tend to undergo exothermic unimolar decompositions at high rates. Thus, high chemical instability may sometimes parallel unimolar decompositions at high rates.
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The structures of acceptors play a critical role in the rate and stereoselectivity of glycosylations. Generally, the unprotected hydroxyl groups are less reactive when they are between bulky protecting groups. That is the reason why the hydroxyl group at OH-4 in pyranosides is unreactive. Hyperconjugation is involved when OH-4 is anti-periplanar to the ring oxygen, which can also reduce its reactivity.
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Greenwood and Earnshaw, pp. 412–16 Given the great reactivity of atomic nitrogen, elemental nitrogen usually occurs as molecular N2, dinitrogen. This molecule is a colourless, odourless, and tasteless diamagnetic gas at standard conditions: it melts at −210 °C and boils at −196 °C. Dinitrogen is mostly unreactive at room temperature, but it will nevertheless react with lithium metal and some transition metal complexes.
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If chloride ions have penetrated beyond the surface more rigorous treatment is required. This typically involves soaking in acetone to displace any water in the specimen. Then soaking in a benzotriazole (BTA)–ethanol solution to chelate the copper and make it unreactive. Pits and holes may be filled with zinc powder, which is then painted over with shellac coloured to look like the specimen.
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H and N. Both are relatively unreactive colourless diatomic gases, with comparably high ionization energies (1312.0 and 1402.3 kJ/mol), each having half-valence subshells, 1s and 2p respectively. Like the reactive azide N3− anion, inter- electron repulsions in the H− hydride anion (with its single nuclear charge) make ionic hydrides highly reactive. Unusually for nonmetals, the two elements are known in cationic forms.
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Lime kilns are used to produce Calcium oxide or quicklime by calcinating limestone. The reaction involved takes place at around 900 °C, but a temperature around 1000 °C is usually used to make the reaction proceed more quickly.Parkes, G.D. and Mellor, J.W. (1939). Mellor's Modern Inorganic Chemistry London: Longmans, Green and Co. Excessive temperature is avoided because it produces unreactive or "dead-burned" lime.
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In case of multiple carbonyl types in one molecule, one can expect the most electrophilic carbonyl carbon to react first. Acyl chlorides and carboxylic anhydrides react fastest, followed by aldehydes and ketones. Esters react much more slowly and amides are almost completely unreactive due to resonance of the amide nitrogen towards the carbonyl group. This reactivity difference allows chemoselectivity when a reactant contains multiple carbonyl groups.
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Although often compared with benzene, borazine is far more reactive. With hydrogen chloride it forms an adduct, whereas benzene is unreactive toward HCl. Polyborazylene :B3N3H6 \+ 3 HCl → B3N3H9Cl3 :Addition reaction of borazine with hydrogen chloride :B3N3H9Cl3 \+ NaBH4 → (BH4N)3 :Reduction with sodium borohydride The addition reaction with bromine does not require a catalyst. Borazines undergo nucleophilic attack at boron and electrophilic attack at nitrogen.
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In recent decades, the existence of the infrared atmospheric window has become threatened by the development of highly unreactive gases containing bonds between fluorine and carbon, sulfur or nitrogen. The impact of these compounds was first discovered by Indian–American atmospheric scientist Veerabhadran Ramanathan in 1975,Ramanathan, Veerabhadran; 'Greenhouse Effect Due to Chlorofluorocarbons: Climatic Implications'; Science, vol. 190, no. 4209 (October 3, 1975), pp.
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Reactions with elemental fluorine are often sudden or explosive. Many substances that are generally regarded as unreactive, such as powdered steel, glass fragments, and asbestos fibers, are readily consumed by cold fluorine gas. Wood and even water burn with flames when subjected to a jet of fluorine, without the need for a spark. Reactions of elemental fluorine with metals require different conditions that depend on the metal.
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"Image of calix-[4]-arene carceplex" A carceplex is a class of chemical structures in the carcerand family that are hinged, and can be closed using reagents that react with the carceplex and trap precursors of reactive intermediates, and are unreactive with the trapped precursor or reactive intermediate. This is useful for determining the spectroscopic and crystallographic properties of reactive intermediates in relative isolation, particularly compounds prone to dimerization like cyclobutadiene.
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Suicide inhibitors are used in what is called "rational drug design" where the aim is to create a novel substrate, based on already known mechanisms and substrates. The main goal of this approach is to create substrates that are unreactive until within that enzyme's active site and at the same time being highly specific. Drugs based on this approach have the advantage of very few resulting side effects.
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The dimethylated lysine's acetylated and isotopically labeled protein peptides and neo(new)-N-terminal peptides are unreactive and remain unbound and can be separated from the poly-internal tryptic peptide complexes using ultrafiltration. # The eluted unbound proteins are highly concentrated with the N-terminal peptides and neo-N-terminal peptides. # This eluted sample is then quantified and analysis completed by MS/MS. # The final step in TAILS involves bioinformatics.
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The next step in crossover experiment design is to propose labeled reactants. For a non-isotopic labeling method the smallest perturbation to the system will be by addition of a methyl group at an unreactive position. Predicting the products given by each mechanism will show whether or not a given crossover experiment design can distinguish between the mechanisms in question. This is particularly relevant when employing an isotopic label.
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The quadricyclane ligation utilizes a highly strained quadricyclane to undergo [2+2+2] cycloaddition with π systems. 600px Quadricyclane is abiotic, unreactive with biomolecules (due to complete saturation), relatively small, and highly strained (~80 kcal/mol). However, it is highly stable at room temperature and in aqueous conditions at physiological pH. It is selectively able to react with electron-poor π systems but not simple alkenes, alkynes, or cyclooctynes.
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Although the sulfur atom is relatively unreactive, the flanking carbon centers, the 2- and 5-positions, are highly susceptible to attack by electrophiles. Halogens give initially 2-halo derivatives followed by 2,5-dihalothiophenes; perhalogenation is easily accomplished to give C4X4S (X = Cl, Br, I). Thiophene brominates 107 times faster than does benzene. Chloromethylation and chloroethylation occur readily at the 2,5-positions. Reduction of the chloromethyl product gives 2-methylthiophene.
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As a residue in a peptide, it is generated by a post translational modification. The required precursors are serine or cysteine residues, which undergo enzyme-mediated loss of water and hydrogen sulfide, respectively. Most amino acid residues are unreactive toward nucleophiles, but those containing dehydroalanine or some other dehydroamino acids are exceptions. These are electrophilic due to the α,β-unsaturated carbonyl, and can, for example, alkylate other amino acids.
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The reaction was initially demonstrated using a ketone as the directing group, but other functional groups have been reported, including esters, imines, nitriles, and imidates. Murai reactions have also been reported with disubstituted alkynes. bidentate directing group allow ortho alkylation of aromatic rings with α,β-unsaturated ketones, which typically are unreactive in Murai reactions. Early examples of the reaction suffered from side products of alkylation at both ortho positions.
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With rare exceptions, H2 is unreactive toward organic compounds in the absence of metal catalysts. The unsaturated substrate is chemisorbed onto the catalyst, with most sites covered by the substrate. In heterogeneous catalysts, hydrogen forms surface hydrides (M-H) from which hydrogens can be transferred to the chemisorbed substrate. Platinum, palladium, rhodium, and ruthenium form highly active catalysts, which operate at lower temperatures and lower pressures of H2.
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Amyl nitrite is a chemical compound with the formula C5H11ONO. A variety of isomers are known, but they all feature an amyl group attached to the nitrite functional group. The alkyl group is unreactive and the chemical and biological properties are mainly due to the nitrite group. Like other alkyl nitrites, amyl nitrite is bioactive in mammals, being a vasodilator, which is the basis of its use as a prescription medicine.
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As a metalloid the chemistry of silicon is largely covalent in nature, noting it can form alloys with metals such as iron and copper. The common oxide of silicon (SiO2) is weakly acidic. Germanium Germanium is a shiny, mostly unreactive grey-white solid with a density of 5.323 g/cm3 (about two-thirds that of iron), and is hard (MH 6.0) and brittle. It melts at 938.25 °C (cf.
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Hutchinson's pupil is a clinical sign in which the pupil on the side of an intracranial mass lesion is dilated and unreactive to light, due to compression of the oculomotor nerve on that side. The sign is named after Sir Jonathan Hutchinson. These can be due to concussion injury to the brain and is associated with subdural haemorrhage and unconsciousness. The parasympathetic fibers to the pupil are responsible for pupillary constriction.
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Oxygen exists as a ground state triplet state, which is relatively unreactive and needs free radicals or very electron-rich substrates such as deprotonated lignin phenolic groups. The production of these phenoxide groups requires that delignification with oxygen be carried out under very basic conditions (pH >12). The reactions involved are primarily single electron (radical) reactions. Oxygen opens rings and cleaves sidechains giving a complex mixture of small oxygenated molecules.
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Spectrum of the blue flame from a butane torch showing excited molecular radical band emission and Swan bands A familiar radical reaction is combustion. The oxygen molecule is a stable diradical, best represented by ·O-O·. Because spins of the electrons are parallel, this molecule is stable. While the ground state of oxygen is this unreactive spin- unpaired (triplet) diradical, an extremely reactive spin-paired (singlet) state is available.
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Noble gas compounds are chemical compounds that include an element from the noble gases, group 18 of the periodic table. Although the noble gases are generally unreactive elements, many such compounds have been observed, particularly involving the element xenon. From the standpoint of chemistry, the noble gases may be divided into two groups: the relatively reactive krypton (ionisation energy 14.0 eV), xenon (12.1 eV), and radon (10.7 eV) on one side, and the very unreactive argon (15.8 eV), neon (21.6 eV), and helium (24.6 eV) on the other. Consistent with this classification, Kr, Xe, and Rn form compounds that can be isolated in bulk at or near standard temperature and pressure (at least in principle for the highly radioactive radon), whereas He, Ne, Ar have been observed to form true chemical bonds using spectroscopic techniques, but only when frozen into a noble gas matrix at temperatures of 40 K or lower, in supersonic jets of noble gas, or under extremely high pressures with metals.
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The use of activated anthranilic acid derivatives facilitates the preparation of the amides in those cases where the amines are either unreactive or difficult to obtain. Metolazone center: Thus, reaction of (1) with phosgene gives the reactive the isatoic anhydride (2). Condensation of that with ortho-toluidine leads to the acylation product (3) formed with a simultaneous loss of carbon dioxide. This is then converted to the quinazolone (4) by heating with acetic anhydride.
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Further impurities, such as iron, nickel, gallium and tungsten compounds, can be introduced if unreacted fluorine is recycled. The technical-grade fluorine is purified by reacting it with MnF3 to form manganese tetrafluoride. As this stage, and heavy metals present will form involatile complex fluorides, while the HF and O2 are unreactive. Once the MnF3 has been converted, the excess gas is vented for recycling, carrying the remaining gaseous impurities with it.
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Because of the sensitivity of potassium to water and air, air-free techniques are normally employed for handling the element. It is unreactive toward nitrogen and saturated hydrocarbons such as mineral oil or kerosene. It readily dissolves in liquid ammonia, up to 480 g per 1000 g of ammonia at 0°C. Depending on the concentration, the ammonia solutions are blue to yellow, and their electrical conductivity is similar to that of liquid metals.
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Argon is produced industrially by the fractional distillation of liquid air. Argon is mostly used as an inert shielding gas in welding and other high-temperature industrial processes where ordinarily unreactive substances become reactive; for example, an argon atmosphere is used in graphite electric furnaces to prevent the graphite from burning. Argon is also used in incandescent, fluorescent lighting, and other gas-discharge tubes. Argon makes a distinctive blue-green gas laser.
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Magnesium oxide is produced by the calcination of magnesium carbonate or magnesium hydroxide. The latter is obtained by the treatment of magnesium chloride solutions, typically seawater, with lime. :Mg2+ \+ Ca(OH)2 → Mg(OH)2 \+ Ca2+ Calcining at different temperatures produces magnesium oxide of different reactivity. High temperatures 1500 – 2000 °C diminish the available surface area and produces dead-burned (often called dead burnt) magnesia, an unreactive form used as a refractory.
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Molybdenum (Mo), the most common transition metal ion in modern seawater, is also used to look for evidence for euxinia. Weathering of rocks provides an input of MoO42– into oceans. Under oxic conditions, MoO42– is very unreactive, but in modern euxinic environments such as the Black Sea, molybdenum precipitates out as oxythiomolybdate (MoO4−xSx2– ). The isotope ratio for Molybdenum (δ97/95 Mo) in euxinic sediments appears to be higher than in oxic conditions.
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Microtubules and microfilaments were known, and they established that microtubules always reacted with antibodies to tubulins while microfilaments always reacted with antibodies to actin. In the course of their studies, they also found intermediate filaments, slightly thicker than microfilaments, and unreactive to actin antibodies. They developed new antibodies against proteins of the microtubules, intermediate filaments, and microfilaments to use as reagents in examining many types of cells. Many of their antibodies have been licensed to companies for commercial development.
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Metal pots are made from a narrow range of metals because pots and pans need to conduct heat well, but also need to be chemically unreactive so that they do not alter the flavor of the food. Most materials that are conductive enough to heat evenly are too reactive to use in food preparation. In some cases (copper pots, for example), a pot may be made out of a more reactive metal, and then tinned or clad with another.
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In addition, duct engines use air as an oxidant, which contains 78% largely unreactive nitrogen, which dilutes the reaction and lowers the temperatures. Rockets have none of these inherent combustion temperature limiters. The temperatures reached by rocket exhaust often substantially exceed the melting points of the nozzle and combustion chamber materials (about 1,200 K for copper). Most construction materials will also combust if exposed to high temperature oxidizer, which leads to a number of design challenges.
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In deposit, the spores appear white. Individual spores are ellipsoid to tear-shaped in profile, obovoid to ellipsoid or roughly cylindric in face or back view, with dimensions of 4.8–6.4 by 2–2.8 (sometimes up to 3.5) µm. They are smooth, inamyloid, and acyanophilous (unreactive to staining with Melzer's reagent and methyl blue, respectively). The basidia (spore-bearing cells of the hymenium) are roughly club-shaped, four-spored, and measure 17.5–21 by 4.8–5.6 µm.
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Jørgensen prepared numerous examples of coordination complexes, providing an experimental foundation for Blomstrand-Jørgensen chain theory and for Alfred Werners coordination theory (1893). In developing the theory, Blomstrand reconciled the low reactivity of the ammonia molecules present in metal ammine complexes by theorizing that the ammonia molecules were chemically linked together in a chain, rendering them chemically unreactive. This chain theory was superseded in 1893, almost 25 years later, when Alfred Werner proposed his coordination theory.
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TLC plates are usually commercially available, with standard particle size ranges to improve reproducibility. They are prepared by mixing the adsorbent, such as silica gel, with a small amount of inert binder like calcium sulfate (gypsum) and water. This mixture is spread as a thick slurry on an unreactive carrier sheet, usually glass, thick aluminum foil, or plastic. The resultant plate is dried and activated by heating in an oven for thirty minutes at 110 °C.
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The silyl group is a non-polar and relatively unreactive species and is therefore tolerant of many reagents and reaction conditions that might be incompatible with free alcohols. Consequently, the silyl group also eliminates the need for introduction of hydroxyl protecting groups. In short, by deferring introduction of an alcohol to a late synthetic stage, opting instead to carry through a silane, a number of potential problems experienced in total syntheses can be mitigated or avoided entirely.
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Ascorbate can terminate these chain radical reactions by electron transfer. The oxidized forms of ascorbate are relatively unreactive and do not cause cellular damage. However, being a good electron donor, excess ascorbate in the presence of free metal ions can not only promote but also initiate free radical reactions, thus making it a potentially dangerous pro-oxidative compound in certain metabolic contexts. Ascorbic acid and its sodium, potassium, and calcium salts are commonly used as antioxidant food additives.
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In the upper atmosphere, the photodissociation of normally unreactive chlorofluorocarbons (CFCs) by solar ultraviolet radiation is an important source of radicals (see eq. 1 below). These reactions give the chlorine radical, Cl•, which catalyzes the conversion of ozone to O2, thus facilitating ozone depletion (– below). Such reactions cause the depletion of the ozone layer, especially since the chlorine radical is free to engage in another reaction chain; consequently, the use of chlorofluorocarbons as refrigerants has been restricted.
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An important implication of encapsulating a molecule at this level is that the guest is prevented from contacting other molecules that it might otherwise react with. Thus the encapsulated molecule behaves very differently from the way it would when in solution. The guest molecule tends to be extremely unreactive and often has much different spectroscopic signatures. Compounds normally highly unstable in solution, such as arynes or cycloheptatetraene, have been successfully isolated at room temperature when molecularly encapsulated.
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Both DCPD and Grubbs' catalyst are imbedded in an epoxy resin. The monomer on its own is relatively unreactive and polymerization does not take place. When a microcrack reaches both the capsule containing DCPD and the catalyst, the monomer is released from the core–shell microcapsule and comes in contact with exposed catalyst, upon which the monomer undergoes ring opening metathesis polymerization (ROMP). The metathesis reaction of the monomer involves the severance of the two double bonds in favor of new bonds.
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Lead has the highest atomic number of any stable element and three of its isotopes are endpoints of major nuclear decay chains of heavier elements. Lead is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its amphoteric nature; lead and lead oxides react with acids and bases, and it tends to form covalent bonds. Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group.
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The C–B bond is therefore a useful intermediate as a bond that replaces a typically unreactive C–H bond. Organoboron compounds are organic compounds containing a carbon-boron bond. Organoboron compounds have broad applications for chemical synthesis because the C–B bond can easily be converted into a C–X (X = Br, Cl), C–O, C–N, or C–C bond. Because of the versatility of the C–B bond numerous processes have been developed to incorporate them into organic compounds.
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The turbopause, also known as the homopause, marks the altitude in an atmosphere below which turbulent mixing dominates. Mathematically, it is defined as the point where the coefficient of eddy diffusion is equal to the coefficient of molecular diffusion. The region below the turbopause is known as the homosphere, where the atmosphere is well mixed for chemical species which have long mean residence times. Highly reactive chemicals tend to have variable concentration throughout the atmosphere, while unreactive species have more homogeneous concentrations.
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Supramolecular containers do not only have an application in catalysis but also in the opposite, namely, inhibition. A container molecule could encapsulate a guest molecule and thus subsequently renders the guest unreactive. A mechanism of inhibition could either be that the substrate is completely isolated from the reagent or that the container molecule destabilize the transition state of the reaction. Nitschke and coworkers invented a self-assembly M4L6 supramolecular host with a tetrahedral hydrophobic cavity that can encapsulate white phosphorus.
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Consecutively, the probe is incubated in a SAM to make the surface of the probe that is unoccupied unreactive to target or further aptamer binding. The optimized SAM thickness is thick enough for the surface to be passivated against target binding and thin enough to transfer electrons from the redox reporter to the electrode. SAM thickness can be measured as length. It has been reported that cocaine E-AB sensors generate more signal when the SAM is thinner and therefore more conductive.
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Un-dyed, unscented paraffin candles are odorless and bluish-white. Paraffin wax was first created by Carl Reichenbach in Germany in 1830 and marked a major advancement in candlemaking technology, as it burned more cleanly and reliably than tallow candles and was cheaper to produce. In chemistry, paraffin is used synonymously with alkane, indicating hydrocarbons with the general formula CnH2n+2. The name is derived from Latin parum ("barely") + affinis, meaning "lacking affinity" or "lacking reactivity", referring to paraffin's unreactive nature.
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It also means molecular oxygen is relatively unreactive at room temperature except in the presence of a catalytic heavy atom such as iron or copper. Combustion consists of various radical chain reactions that the singlet radical can initiate. The flammability of a given material strongly depends on the concentration of radicals that must be obtained before initiation and propagation reactions dominate leading to combustion of the material. Once the combustible material has been consumed, termination reactions again dominate and the flame dies out.
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Instead, the byproduct, diazonium-methyl from the other diazomethane molecule, can be attacked by the chloride to produce chloromethane. The unreactive diazoketone can be re-activated and reacted by treatment with hydrogen chloride to give the normal Nierenstein product. The Nierenstein reaction mechanism In some cases, even limiting the amount of diazomethane gives a reaction process that stalls via the neutral diazoketone pathway, requiring the addition of HCl gas to rescue it.McPhee, W. D; Klingsberg, E. Organic Syntheses, Coll. Vol.
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Trifluoroperacetic acid (trifluoroperoxyacetic acid, TFPAA) is an organofluorine compound, the peroxy acid analog of trifluoroacetic acid, with the condensed structural formula . It is a strong oxidizing agent for organic oxidation reactions, such as in Baeyer–Villiger oxidations of ketones. It is the most reactive of the organic peroxy acids, allowing it to successfully oxidise relatively unreactive alkenes to epoxides where other peroxy acids are ineffective. It can also oxidise the chalcogens in some functional groups, such as by transforming selenoethers to selones.
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The Theory of NMR – Solvents for NMR spectroscopy In addition, it is chemically unreactive and unlikely to exchange its deuterium with its solute, and its low boiling point allows for easy sample recovery. The properties of CDCl3 are virtually identical to those of regular chloroform, although biologically, it is slightly less toxic to the liver than CHCl3, due to its C–D bond, which is stronger than a C–H bond, making it somewhat less prone to form the destructive trichloromethyl radical (•CCl3).
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The parent compound ruthenocene is unreactive because it is coordinatively saturated and contains no reactive groups. Shvo's catalyst ([Ph4(η5-C4CO)]2H]}Ru2(CO)4(μ-H)) is also coordinatively saturated, but features reactive OH and RuH groups that enable it to function in transfer hydrogenation. It is used in hydrogenation of aldehydes, ketones, via transfer hydrogenation, in disproportionation of aldehydes to esters and in the isomerization of allylic alcohols. Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium features a reactive chloro group, which is readily substituted by organic substrates.
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Fullerenes are stable, but not totally unreactive. The sp2-hybridized carbon atoms, which are at their energy minimum in planar graphite, must be bent to form the closed sphere or tube, which produces angle strain. The characteristic reaction of fullerenes is electrophilic addition at 6,6-double bonds, which reduces angle strain by changing sp2-hybridized carbons into sp3-hybridized ones. The change in hybridized orbitals causes the bond angles to decrease from about 120° in the sp2 orbitals to about 109.5° in the sp3 orbitals.
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Nitrous oxide is a greenhouse gas with a global warming potential 298 times that of carbon dioxide. Global warming potential is a way to compare global warming impacts of different gases relative to carbon dioxide emissions. Since nitrous oxide has such a high global warming potential, it is able to warm the earth more effectively compared to other greenhouse gases. Although generally unreactive in the troposphere, nitrous oxide is destroyed during photolysis or reactions with excited oxygen atoms and catalyzes the destruction of ozone in the stratosphere.
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Kiplinger received her B.S. degree in Chemistry from the University of Colorado at Colorado Springs in 1990. Under the guidance of Professor Ruminiski, Kiplinger has published several papers reporting coordination chemistry of iron and ruthenium featuring multidentate pyrazine-based ligands. Kiplinger did her graduate studies at the University of Utah working with Professor Thomas Richmond. Her work focused on using organometallic species to break carbon- fluorine bonds in perfluoroalkanes, which are usually unreactive due to fluorine’s high electronegativity and the strength of the carbon-fluorine bond.
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In bacteria, acylating acetaldehyde dehydrogenase forms a bifunctional heterodimer with metal-dependent 4-hydroxy-2-ketovalerate aldolase. Utilized in the bacterial degradation of toxic aromatic compounds, the enzyme’s crystal structure indicates that intermediates are shuttled directly between active sites through a hydrophobic intermediary channel, providing an unreactive environment in which to move the reactive acetaldehyde intermediate from the aldolase active site to the acetaldehyde dehydrogenase active site. Such communication between proteins allows for the efficient transfer substrates from one active site to the next.
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Generation of a vinyl cation reactive intermediate. Adapted from Vinyl cations have been observed as reactive intermediates during solvolysis reactions. Consistent with SN1 chemistry, these reactions follow first order kinetics. Generally, vinylic halides are unreactive in solution: silver nitrate does not precipitate silver halides in the presence of vinyl halides, and this fact was historically used to dispute the existence of the vinyl cation species. The introduction of “super” Leaving group in the 1970s first allowed for the generation of vinyl cation reactive intermediates with appreciable lifetimes.
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Fischer esterification is an example of nucleophilic acyl substitution based on the electrophilicity of the carbonyl carbon and the nucleophilicity of an alcohol. However, carboxylic acids tend to be less reactive than esters as electrophiles. Additionally, in dilute neutral solutions they tend to be deprotonated anions (and thus unreactive as electrophiles). Though very kinetically slow without any catalysts (most esters are metastable), pure esters will tend to spontaneously hydrolyse in the presence of water, so when carried out "unaided", high yields for this reaction is quite unfavourable.
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Evidence also exists for a carbocation based mechanism of dealkylation similar to an SN1 reaction, where the R1 group initially dissociates from the phosphonium salt followed by attack of the anion. Phosphite esters with tertiary alkyl halide groups can undergo the reaction, which would be unexpected if only an SN2 mechanism was operating. Further support for this SN1 type mechanism comes from the use of the Arbuzov reaction in the synthesis of neopentyl halides, a class of compounds that are notoriously unreactive towards SN2 reactions.
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Unit cell ball-and-stick model of lithium nitride. On the basis of size a tetrahedral structure would be expected, but that would be geometrically impossible: thus lithium nitride takes on this unique crystal structure. Lithium, the lightest of the alkali metals, is the only alkali metal which reacts with nitrogen at standard conditions, and its nitride is the only stable alkali metal nitride. Nitrogen is an unreactive gas because breaking the strong triple bond in the dinitrogen molecule (N2) requires a lot of energy.
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If all three lone pairs are included for a bond order of three than the M-O bond distance contracts further and since the oxygen is a sp center the M-O-R bond angle is 180˚ or linear. Similarly with the imidos are commonly referred to as either bent (sp2) or linear (sp). Even the oxo can be sp2 or sp hybridized. The triply bonded oxo, similar to carbon monoxide, is partially positive at the oxygen atom and unreactive towards Brønsted acids at the oxygen atom.
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The target of cyclopropanation also varies depending on the conditions used. The Simmons- Smith reaction adds to alkenes while the Buchner ring expansion allows addition to typically unreactive arenes. The Buchner ring expansion is useful because it gives cycloheptatrienes as the ring opened products, which are found in the core of some natural products, such as azulenes. An important consideration in these ring expansions is the ring opening to an expanded ring and not an exocyclic group on the original ring or an unopenable product.
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Noble gasses are particularly useful for these experiments because they are easy to handle, unreactive and relatively inexpensive. One such experiment was being carried out on the Bevalac at the Lawrence Berkeley National Laboratory using Argon 40 accelerated to 1.8 GeV and then smashed into a copper target backed with a nuclear emulsion detector. It was here that the anomalons were first observed. While studying the results of these experiments, a number of very short tracks were discovered, penetrating only a short distance into the emulsion.
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Living polymerization was demonstrated by Michael Szwarc in 1956 in the anionic polymerization of styrene with an alkali metal / naphthalene system in tetrahydrofuran (THF). Szwarc showed that electron transfer occurred from radical anion of naphthalene to styrene. The initial radical anion of styrene converts to a dianion (or equivalently disodio-) species, which rapidly added styrene to form a "two – ended living polymer." An important aspect of his work, Szwarc employed the aprotic solvent tetrahydrofuran, which dissolves but is otherwise unreactive toward the organometallic intermediates.
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The hexafluorides have a wide range of chemical reactivity. Sulfur hexafluoride is nearly inert and non-toxic due to steric hindrance (the six fluorine atoms are arranged so tightly around the sulfur atom that it is extremely difficult to attack the bonds between the fluorine and sulfur atoms). It has several applications due to its stability, dielectric properties, and high density. Selenium hexafluoride is nearly as unreactive as SF6, but tellurium hexafluoride is not very stable and can be hydrolyzed by water within 1 day.
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Tin(IV) fluoride is a chemical compound of tin and fluorine with the chemical formula SnF4 and is a white solid with a melting point above 700 °C. SnF4 can be prepared by the reaction of tin metal with fluorine gas: :Sn + 2F2 → SnF4 However, a passivating metal fluoride layer will be created and the surface will eventually become unreactive. An alternative synthesis is the reaction of SnCl4 with anhydrous hydrogen fluoride: :SnCl4 \+ 4HF → SnF4 \+ 4HCl With alkali metal fluorides (e.g. KF) hexafluorostannates are produced (e.g.
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Helium is the smallest and the lightest noble gas and one of the most unreactive elements, so it was commonly considered that helium compounds cannot exist at all, or at least under normal conditions. Helium's first ionization energy of 24.57 eV is the highest of any element. Helium has a complete shell of electrons, and in this form the atom does not readily accept any extra electrons nor join with anything to make covalent compounds. The electron affinity is 0.080 eV, which is very close to zero.
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Monazite is a chemically unreactive mineral that is found as yellow or brown sand; its low reactivity makes it difficult to extract thorium from it. Allanite (chiefly silicates-hydroxides of various metals) can have 0.1–2% thorium and zircon (chiefly zirconium silicate, ZrSiO4) up to 0.4% thorium. Thorium dioxide occurs as the rare mineral thorianite. Due to its being isotypic with uranium dioxide, these two common actinide dioxides can form solid-state solutions and the name of the mineral changes according to the ThO2 content.
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MTSL (S-(1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-3-yl)methyl methanesulfonothioate) is an organosulfur compound that is used as a nitroxide spin label.Christian Altenbach, Kyoung-Joon Oh, René J. Trabanino, Kálmán Hideg, Wayne L. Hubbell "Estimation of Inter-Residue Distances in Spin Labeled Proteins at Physiological Temperatures: Experimental Strategies and Practical Limitations" Biochemistry, 2001, volume 40, pp 15471–15482. MTSL is bifunctional, consisting of the nitroxide and the thiosulfonate ester functional groups. The nitroxide label is sterically protected, so it is relatively unreactive.
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2-Chloro- phenylamines are completely unreactive. In addition to these three components, the reaction was optimized in the presence of 0.05 molar equivalents (5 mol%) of a catalyst, copper(I) chloride, and 5 mol% of ligand, TMEDA (tetramethylethylenediamine). After heating these components at 120 °C for 12 hours in DMSO, the direct etonitazene precursor, 2-(4-Ethoxybenzyl)-5-nitro-1H-benzoimidazole, was formed in an approx 80-90% yield. The secondary amine nitrogen of 2-(4-Ethoxybenzyl)-5-nitro-1H-benzoimidazole was then alkylated with (2-Chloroethyl)diethylamine to form etonitazene.
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In chemistry, the term chemically inert is used to describe a substance that is not chemically reactive. From a thermodynamic perspective, a substance is inert, or nonlabile, if it is thermodynamically unstable (positive standard Gibbs free energy of formation) yet decomposes at a slow, or negligible rate. Most Group 8 or 18 elements that appear in the last column of the periodic table (Helium, Neon, Argon, Krypton, Xenon and Radon) are classified as inert (or unreactive). These elements are stable in their naturally occurring form (gaseous form) and they are called inert gases.
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Barbituric acid is the parent compound of barbiturate drugs although barbituric acid itself is not pharmacologically active. Barbiturates were synthesized in 1864 by Adolf von Baeyer by combining urea and malonic acid (Figure 5). A synthesis process was later developed and perfected by French chemist Edouard Grimaux in 1879, making possible the subsequent widespread development of barbiturate derivatives. Malonic acid was later replaced by diethyl malonate, as using the ester avoids the need to deal with the acidity of the carboxylic acid and its unreactive carboxylate (see figure 6).
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Because DNA transposition events are inherently mutagenic, the low activity of transposases is necessary to reduce the risk of causing a fatal mutation in the host, and thus eliminating the transposable element. One of the reasons Tn5 is so unreactive is because the N- and C-termini are located in relatively close proximity to one another and tend to inhibit each other. This was elucidated by the characterization of several mutations which resulted in hyperactive forms of transposases. One such mutation, L372P, is a mutation of amino acid 372 in the Tn5 transposase.
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While organic photoredox catalysts were dominant throughout the 1990s and early 2000s, soluble transition-metal complexes are more commonly used today. Schematic diagram of [Ru(bipy)3]2+, a typical photoredox catalyst Study of this branch of catalysis led to the development of new methods to accomplish known and new chemical transformations. Photoredox catalysts are usually far less toxic than traditional reagents used to generate free radicals, such as organotin compounds. Furthermore, photoredox catalysts generate potent redox agents when exposed to light, they are unreactive under normal conditions.
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The neutral molecule appears to be planar, with three-fold rotational symmetry (symmetry group D3h); or possibly a resonance between three Y-shaped molecules. The radical does not react directly with water, and is relatively unreactive towards closed-shell molecules, as opposed to isolated atoms and other radicals. It is decomposed by light of certain wavelenths into nitric oxide and oxygen . The absorption spectrum of has a broad band for light with wavelengths from about 500 to 680 nm, with three salient peaks in the visible at 590, 662, 623 nm.
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Alternatively, the original West/Denk NHSi [tBuN-CH=CH-tBuN]Si is exceptionally stable even after heating for 4 months at 150 °C dissolved in toluene in a sealed NMR tube. It is also unreactive with Lewis bases and triethylsilane a silylene scavengers, but it does react with air and water (see below) and decomposes at its melting point 220 °C. On the other hand, the saturated NHSi with no backbone substitutions, [tBuN-CH2CH2-tBuN]Si:, is far more reactive as a Lewis acid and far less stable, decomposing at 25 °C.
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A: test-tube, B: dilute alkali, C: U-shaped glass tube, D: platinum electrode Argon (Greek , neuter singular form of meaning "lazy" or "inactive") is named in reference to its chemical inactivity. This chemical property of this first noble gas to be discovered impressed the namers. An unreactive gas was suspected to be a component of air by Henry Cavendish in 1785. Argon was first isolated from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water, and nitrogen from a sample of clean air.
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In addition to control of temperature (mentioned above), the main requirement is to obtain a consistent fineness of the product. From the earliest times, fineness was measured by sieving the cement. As cements have become finer, the use of sieves is less applicable, but the amount retained on a 45 μm sieve is still measured, usually by air-jet sieving or wet-sieving. The amount passing this sieve (typically 95% in modern general-purpose cements) is related to the overall strength-development potential of the cement, because the larger particles are essentially unreactive.
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Like other alkanes, pentanes are largely unreactive at standard room temperature and conditions - however, with sufficient activation energy (e.g., an open flame), they readily oxidize to form carbon dioxide and water: :C5H12 \+ 8 O2 → 5 CO2 \+ 6 H2O + heat/energy Like other alkanes, pentanes undergo free radical chlorination: :C5H12 \+ Cl2 → C5H11Cl + HCl Such reactions are unselective; with n-pentane, the result is a mixture of the 1-, 2-, and 3-chloropentanes, as well as more highly chlorinated derivatives. Other radical halogenations can also occur. Pentane is a component of exhaled breath for some individuals.
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Silicon has a blue-grey metallic lustre. Silicon is a metallic-looking relatively unreactive solid with a density of 2.3290 g/cm3, and is hard (MH 6.5) and brittle. It melts at 1414 °C (cf. steel ~1370 °C) and boils at 3265 °C. Silicon has a diamond cubic structure (CN 4). It is a semiconductor with a band gap of about 1.11 eV. Silicon has a moderate ionisation energy (786.5 kJ/mol), moderate electron affinity (134 kJ/mol), and moderate electronegativity (1.9). It is a poor oxidising agent (Si + 4e → Si4 = –0.147 at pH 0).
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In chemistry, metal vapor synthesis (MVS) is a method for preparing metal complexes by combining freshly produced metal atoms or small particles with ligands. In contrast to the high reactivity of such freshly produced metal atoms, bulk metals typically are unreactive toward neutral ligands. The method has been used to prepare compounds that cannot be prepared by traditional synthetic methods, e.g. Ti(η6-toluene)2. The technique relies on a reactor that evaporates the metal, allowing the vapor to impinge on a cold reactor wall that is coated with the organic ligand.
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Tocopherols are radical scavengers, delivering an H atom to quench free radicals. At 323 kJ/mol, the O-H bond in tocopherols is approximately 10% weaker than in most other phenols. This weak bond allows the vitamin to donate a hydrogen atom to the peroxyl radical and other free radicals, minimizing their damaging effect. The thus generated tocopheryl radical is relatively unreactive, but reverts to tocopherol by a redox reaction with a hydrogen donor such as vitamin C. As they are fat-soluble, tocopherols are incorporated into cell membranes, which are protected from oxidative damage.
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MCP 9, 894–911 (2010). Formaldehyde or isobaric tags including Isotope-coded Affinity Tags (ICAT), 4 to 8 plex Isobaric tag for relative and absolute quantification (iTRAQ), or 10plex Tandem mass tags (TMT) block primary amines prior to trypsin digestion of proteome samples. The main step of the process is the negative selection of newly generated trypsin peptides using a specialized polymer. The polymer ignores the unreactive primary amines blocked by their tags, allowing them to be separated from trypsin generated peptides by ultrafiltration for Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS) analysis.
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The binding of C5 is influenced by C6 and C7, components which are thought to act subsequent to it in the complement sequence. In addition, the hemolytic activity of the isolated C5 intermediate complex is exceedingly labile, having an average half-life at 30 °C of only 9 rain. This characteristic distinguishes the C5 step, along with the C2 step, as potentially rate-limiting in the complement reaction. However, unlike C2, C5 remains firmly cell-bound during the decay process and apparently undergoes an alteration in situ which renders it hemolytically unreactive.
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Signs of procyclidine overdose are those of an anticholinergic and include confusion, agitation and sleeplessness that can last up to or more than 24 hours. Pupils become dilated and unreactive to light. Tachycardia (fast heart beat), as well as auditory and visual hallucinations have also been reported. Other known symptoms of overdose are: clumsiness or unsteadiness, being severely drowsy, having a severely dry mouth, nose, or throat, having an altered mood or other mental changes, seizures, being short of breath or having troubled breathing, a dry and warm, flushed skin.
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Bath bombs' primary ingredients are a weak acid and a bicarbonate base. These are unreactive when dry, but react vigorously when dissolved in water to produce their characteristic fizzing over a period of several minutes. This is an acid-base reaction that involves conversion of citric acid and sodium bicarbonate to sodium citrate and carbon dioxide: C5H7O5CO2H (aq.) \+ NaHCO3 (aq.) → C5H7O5CO2−Na+(aq.) \+ H2O(l) \+ CO2 (g) The other ingredients in bath bombs can vary considerably. However, most have scented ingredients as well as dye to impart a pleasant fragrance and color to bathwater.
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Patients with Spina Bifida have a neural tube that has failed to completely form. This is most commonly in the lower back area in the region of the conus medullaris or cauda equina. It, therefore, affects the bowel similarly to a spinal cord injury affecting the lower motor neuron resulting in a flaccid unreactive rectal wall and means the anal sphincter doesn't contract and close therefore leading to stool leakage. Most patients with spina bifida also have hydrocephalus this can result in intellectual deficits so can contribute to faecal incontinence.
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Radical SAM methylases/methyltransferases are one of the largest yet diverse subgroups and are capable of methylating a broad range of unreactive carbon and phosphorus centers. These enzymes are divided into four classes (Class A, B, C and D) with representative methylation mechanisms. The shared characteristic of the three major classes A, B and C is the usage of SAM, split into two distinct roles: one as a source of a methyl group donor, and the second as a source of 5'-dAdo radical. The recently documented class D utilizes a different methylation mechanism.
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Tyrosine residues are relatively unreactive; therefore they have not been a popular targets for bioconjugation. Recent development has shown that the tyrosine can be modified through electrophilic aromatic substitutions (EAS) reactions, and it is selective for the aromatic carbon adjacent to the phenolic hydroxyl group. This becomes particularly useful in the case that cysteine residues cannot be targeted. Specifically, diazonium effectively couples with tyrosine residues (diazonium salt shown as reagent in the first reaction in Figure 3 below), and an electron withdrawing substituent in the 4-position of diazonium salt can effectively increase the efficiency of the reaction.
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A batch of M. pudica were grown and watered daily, and 10-20 pulvini were collected from each group of pulvini reactive to touch, and pulvini unreactive to touch. To further understand the movement of the ions, the upper and lower halves of all collected pulvini underwent separate ion analysis using the x-ray fluorescence spectroscopy method. This method tracked the location of the ions by coloring them each with a different color of fluorescence dye. In terms of calcium concentrations, there was a significant difference in concentration between both halves of the pulvini, in both the reactive and nonreactive pulvini.
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Susan Solomon, an atmospheric chemist at the National Oceanic and Atmospheric Administration (NOAA), proposed that chemical reactions on polar stratospheric clouds (PSCs) in the cold Antarctic stratosphere caused a massive, though localized and seasonal, increase in the amount of chlorine present in active, ozone-destroying forms. The polar stratospheric clouds in Antarctica are only formed when there are very low temperatures, as low as −80 °C, and early spring conditions. In such conditions the ice crystals of the cloud provide a suitable surface for conversion of unreactive chlorine compounds into reactive chlorine compounds, which can deplete ozone easily.
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Often described adjacent or in collaboration with the ML2 model, the reservoir effect describes the scenario in which part of the chiral ligand is allocated to a pool of inactive heterochiral catalytic complexes outside the catalytic cycle. A pool of unreactive heterochiral catalysts, described with an eepool, develops an equilibrium with the catalytically active homochiral complexes, described with an eeeffective. Depending on the concentration of the inactive pool of catalysts, one can calculate the enantiopurity of the active catalyst complexes. The general result of the reservoir effect is an asymmetric amplification, also known as a (+)-NLE.
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The list of elements it sets on fire is diverse, containing hydrogen, potassium, phosphorus, arsenic, antimony, sulfur, selenium, tellurium, bromine, iodine, and powdered molybdenum, tungsten, rhodium, iridium, and iron. An impermeable fluoride layer is formed by sodium, magnesium, aluminium, zinc, tin, and silver, which may be removed by heating. When heated, even such noble metals as palladium, platinum, and gold are attacked and even the noble gases xenon and radon do not escape fluorination. Nickel containers are usually used due to that metal's great resistance to attack by chlorine trifluoride, stemming from the formation of an unreactive nickel fluoride layer.
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Arsenic pentafluoride and antimony pentafluoride form ionic adducts of the form [ClF4]+[MF6]− (M = As, Sb) and water reacts vigorously as follows:Greenwood and Earnshaw, pp. 832–35 :2 H2O + ClF5 ⟶ 4 HF + FClO2 The product, chloryl fluoride, is one of the five known chlorine oxide fluorides. These range from the thermally unstable FClO to the chemically unreactive perchloryl fluoride (FClO3), the other three being FClO2, F3ClO, and F3ClO2. All five behave similarly to the chlorine fluorides, both structurally and chemically, and may act as Lewis acids or bases by gaining or losing fluoride ions respectively or as very strong oxidising and fluorinating agents.
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Controlling gas and vapor concentrations outside the flammable limits is a major consideration in occupational safety and health. Methods used to control the concentration of a potentially explosive gas or vapor include use of sweep gas, an unreactive gas such as nitrogen or argon to dilute the explosive gas before coming in contact with air. Use of scrubbers or adsorption resins to remove explosive gases before release are also common. Gases can also be maintained safely at concentrations above the UEL, although a breach in the storage container can lead to explosive conditions or intense fires.
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Slow cooling of slag melts results in an unreactive crystalline material consisting of an assemblage of Ca-Al-Mg silicates. To obtain a good slag reactivity or hydraulicity, the slag melt needs to be rapidly cooled or quenched below 800 °C in order to prevent the crystallization of merwinite and melilite. To cool and fragment the slag a granulation process can be applied in which molten slag is subjected to jet streams of water or air under pressure. Alternatively, in the pelletization process the liquid slag is partially cooled with water and subsequently projected into the air by a rotating drum.
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In gas chromatography, the mobile phase (or "moving phase") is a carrier gas, usually an inert gas such as helium or an unreactive gas such as nitrogen. Helium remains the most commonly used carrier gas in about 90% of instruments although hydrogen is preferred for improved separations. The stationary phase is a microscopic layer of liquid or polymer on an inert solid support, inside a piece of glass or metal tubing called a column (an homage to the fractionating column used in distillation). The instrument used to perform gas chromatography is called a gas chromatograph (or "aerograph", "gas separator").
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The positive electrode is composed mostly of materials in the solid state, which reduces the likelihood of corrosion, improving safety. Its specific energy is 100 Wh/kg; specific power is 150 W/kg. The β-alumina solid ceramic is unreactive to sodium metal and sodium aluminum chloride. Lifetimes of over 2,000 cycles and twenty years have been demonstrated with full-sized batteries, and over 4,500 cycles and fifteen years with 10- and 20-cell modules. For comparison, LiFePO4 lithium iron phosphate batteries store 90–110 Wh/kg, and the more common LiCoO2 lithium-ion batteries store 150–200 Wh/kg.
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Watch glass with two grams of chromium(III) picolinate Skeletal stick model (hydrogen atoms omitted) of the chromium(III) picolinate complex Chromium(III) picolinate is a pinkish-red compound and was first reported in 1917. It is poorly soluble in water, having a solubility of 600 μM in water at near neutral pH. Similar to other chromium(III) compounds, it is relatively inert and unreactive, meaning that this complex is stable at ambient conditions and high temperatures are required to decompose the compound. At lower pH levels, the complex hydrolyzes to release picolinic acid and free Cr3+.
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There is usually little need for alkanes to be synthesized in the laboratory, since they are usually commercially available. Also, alkanes are generally unreactive chemically or biologically, and do not undergo functional group interconversions cleanly. When alkanes are produced in the laboratory, it is often a side-product of a reaction. For example, the use of n-butyllithium as a strong base gives the conjugate acid, n-butane as a side-product: : C4H9Li + H2O → C4H10 \+ LiOH However, at times it may be desirable to make a section of a molecule into an alkane-like functionality (alkyl group) using the above or similar methods.
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The partial charges in the polarized carbon–fluorine bond The carbon–fluorine bond is a polar covalent bond between carbon and fluorine that is a component of all organofluorine compounds. It is one of the strongest single bonds in organic chemistry--behind the B-F single bond, Si-F single bond and the H-F single bond, and relatively short--due to its partial ionic character. The bond also strengthens and shortens as more fluorines are added to the same carbon on a chemical compound. As such, fluoroalkanes like tetrafluoromethane (carbon tetrafluoride) are some of the most unreactive organic compounds.
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Its ideal use would be as a raw starting material for methanol or acetic acid synthesis, with plants built at the source to eliminate the issue of transportation. Methanol, in particular, would be of great use as a potential fuel source, and many efforts have been applied to researching the feasibilities of a methanol economy. The challenges of C-H activation and functionalization present themselves when several factors are taken into consideration. Firstly, the C-H bond is extremely inert and non-polar, with a high bond dissociation energy, making methane a relatively unreactive starting material.
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Bonds to other halogens also absorb in the atmospheric window, though much less strongly. Moreover, the unreactive nature of such compounds that makes them so valuable for many industrial purposes means that they are not removable in the natural circulation of the Earth's lower atmosphere. Extremely small natural sources created by means of radioactive oxidation of fluorite and subsequent reaction with sulfate or carbonate minerals produce via degassing atmospheric concentrations of about 40 ppt for all perfluorocarbons and 0.01 ppt for sulfur hexafluoride,Harnisch, J. and Eisenhauer, A.: 'Natural CF4 and SF6 on Earth', Geophysical Research Letters, vol. 25 (1998), pp.
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The initial compounds have a C5H5 ring on their top and an iridium atom in the center, which is bonded to two hydrogen atoms and a P-PH3 group or to two C-O groups. Reaction with alkane under UV light alters those groups. Carbon–hydrogen bond activation (C–H activation) is an area of research on reactions that cleave carbon–hydrogen bonds, which were traditionally regarded as unreactive. The first reported successes at activating C–H bonds in saturated hydrocarbons, published in 1982, used organometallic iridium complexes that undergo an oxidative addition with the hydrocarbon.
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Though SO2 too passes through the tower it is unreactive and comes out of the absorption tower. This stream of gas containing SO2, after necessary cooling is passed through the catalytic converter bed column again achieving up to 99.8% conversion of SO2 to SO3 and the gases are again passed through the final absorption column thus resulting not only achieving high conversion efficiency for SO2 but also enabling production of higher concentration of sulfuric acid. The industrial production of sulfuric acid involves proper control of temperatures and flow rates of the gases as both the conversion efficiency and absorption are dependent on these.
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The uranium f orbitals interact substantially with the aromatic rings just as the d-orbitals in ferrocene interact with the Cp ligands. Uranocene differs from ferrocene because its HOMO and LUMO are centered on the metal and not on the rings and all reactions thus involve the metal often resulting in ligand - metal cleavage. Uranocenes show ease of reduction of U(IV) compounds to U(III) compounds; otherwise they are fairly unreactive. A close relative that does have sufficient reactivity, obtained by reaction of uranocene with uranium borohydride is the half-sandwich compound (COT)U(BH4)2 discovered in 1983 by the group of M.J. Ephritikhine.
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There are two types of free-radical photoinitators: A two component system where the radical is generated through abstraction of a hydrogen atom from a donor compound (also called co-initiator), and a one- component system where two radicals are generated by cleavage. Examples of each type of free-radical photoinitiator is shown below. Free-rad types of photoinitiators1 Benzophenone, xanthones, and quinones are examples of abstraction type photoinitiators, with common donor compounds being aliphatic amines. The resulting R• species from the donor compound becomes the initiator for the free radical polymerization process, while the radical resulting from the starting photoinitiator (benzophenone in the example shown above) is typically unreactive.
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A liquid metal ion source (LMIS) is an ion source which uses metal that is heated to the liquid state and used to form an electrospray to form ions. An electrospray Taylor cone is formed by the application of a strong electric field and ions are produced by field evaporation at the sharp tip of the cone, which has a high electric field. Ions from a LMIS are used in ion implantation and in focused ion beam instruments. Typically gallium is preferred for its low melting point, low vapor pressure, its relatively unreactive nature, and because the gallium ion is sufficiently heavy for ion milling.
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Penams are reactive towards catalytic cleavage via hydrolysis because of the carbonyl carbon's propensity for nucleophilic attack. This is understood by its partial positive (electrophilic) character that results from the electron density being slightly withdrawn by the carbonyl oxygen atom and, consequently, the lack of conjugation between the nitrogen and carbonyl group. Although amide bonds are typically unreactive to cleavage because of its partial double bond character, the pyramidalization and C-N bond distortion make the amide bond in penams have a single bond character, which is more reactive to cleavage. Also, cleavage of the C-N bond is thermodynamically favorable, since opening of the β-lactam ring reduces ring strain.
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The next year, Ramsay tested a report of American chemist William Francis Hillebrand, who found a steam of an unreactive gas from a sample of uraninite. Wishing to prove it was nitrogen, Ramsay analyzed a different uranium mineral, cleveite, and found a new element, which he named krypton. This finding was corrected by British chemist William Crookes, who matched its spectrum to that of the Sun's helium. Following this discovery, Ramsay, using fractional distillation to separate air, discovered several more such gases in 1898: metargon, krypton, neon, and xenon; detailed spectroscopic analysis of the first of these demonstrated it was argon contaminated by a carbon-based impurity.
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The development of well- defined phosphine- or NHC-ligated gold(I) complexes was an important advance and led to significant increase in interest in the synthetic applications of gold catalysis. Ligated gold(I) complexes are typically prepared and stored as the bench-stable (but unreactive) chlorides, LAuCl, e.g., chloro(triphenylphosphine)gold(I), which are typically activated via halide abstraction with silver salts like AgOTf, AgBF4, or AgSbF6 to generate a cationic gold(I) species. Although the coordinatively unsaturated complex "LAu+" is notionally generated from a LAuCl/AgX mixture, the exact nature of the cationic gold species and the role of the silver salt remains somewhat contentious.
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Mobility refers to the extent to which affect changes during the interview: the affect may be described as fixed, mobile, immobile, constricted/restricted or labile. The person may show a full range of affect, in other words a wide range of emotional expression during the assessment, or may be described as having restricted affect. The affect may also be described as reactive, in other words changing flexibly and appropriately with the flow of conversation, or as unreactive. A bland lack of concern for one's disability may be described as showing la belle indifférence,French: beautiful indifference a feature of conversion disorder, which is historically termed "hysteria" in older texts.
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Due to its resonance stabilization, the peptide bond is relatively unreactive under physiological conditions, even less than similar compounds such as esters. Nevertheless, peptide bonds can undergo chemical reactions, usually through an attack of an electronegative atom on the carbonyl carbon, breaking the carbonyl double bond and forming a tetrahedral intermediate. This is the pathway followed in proteolysis and, more generally, in N-O acyl exchange reactions such as those of inteins. When the functional group attacking the peptide bond is a thiol, hydroxyl or amine, the resulting molecule may be called a cyclol or, more specifically, a thiacyclol, an oxacyclol or an azacyclol, respectively.
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Due to the low heat of process and the relatively unreactive solvent used in the extraction, the fragrant compounds derived often closely resemble the original odour of the raw material. Like solvent extraction, the CO2 extraction takes place at a low temperature, extracts a wide range of compounds, and leaves the aromatics unaltered by heat, rendering an essence more faithful to the original. Since CO2 is gas at normal atmospheric pressure, it also leaves no trace of itself in the final product, thus allowing one to get the absolute directly without having to deal with a concrete. It is a low-temperature process, and the solvents are easily removed.
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In the atmosphere, dinitrogen pentoxide is an important reservoir of the NOx species that are responsible for ozone depletion: its formation provides a null cycle with which NO and NO2 are temporarily held in an unreactive state. Mixing ratios of several ppbv have been observed in polluted regions of the night-time troposphere. Dinitrogen pentoxide has also been observed in the stratosphere at similar levels, the reservoir formation having been postulated in considering the puzzling observations of a sudden drop in stratospheric NO2 levels above 50 °N, the so-called 'Noxon cliff'. Variations in N2O5 reactivity in aerosols can result in significant losses in tropospheric ozone, hydroxyl radicals, and NOx concentrations.
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It forms a relatively large number of compounds, mostly containing fluorine or oxygen. An unusual ion containing xenon is the tetraxenonogold(II) cation, , which contains Xe–Au bonds. This ion occurs in the compound , and is remarkable in having direct chemical bonds between two notoriously unreactive atoms, xenon and gold, with xenon acting as a transition metal ligand. The compound contains a Xe–Xe bond, the longest element-element bond known (308.71 pm = 3.0871 Å). The most common oxide of xenon (XeO3) is strongly acidic. Radon, which is radioactive, has a density of 9.73 × 10−3 g/cm3, liquifies at −61.7 °C, and solidifies at −71 °C.
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She demonstrated infected leaf sap injected into rabbits could produce polyclonal antibodies in rabbit antiserum that were not found in the control (non-infected leaf sap injections). The antibodies were specific to Tobacco mosaic virus, thus identifying and characterizing the virus as a pathogenic agent in tobacco mosaic disease. The specificity of the antibody for Tobacco mosaic virus, being unreactive with other viruses, proved to be a useful tool with which to diagnose a Tobacco mosaic virus infection. It also allowed for the isolation and characterization of unique strains of Tobacco mosaic virus, making it possible for her collaborator, Wendell M. Stanley, to work with a single pure strain.
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Structure of the helium hydride ion, HHe+ Structure of the suspected fluoroheliate anion, OHeF− Helium has a valence of zero and is chemically unreactive under all normal conditions. It is an electrical insulator unless ionized. As with the other noble gases, helium has metastable energy levels that allow it to remain ionized in an electrical discharge with a voltage below its ionization potential. Helium can form unstable compounds, known as excimers, with tungsten, iodine, fluorine, sulfur, and phosphorus when it is subjected to a glow discharge, to electron bombardment, or reduced to plasma by other means. The molecular compounds HeNe, HgHe10, and WHe2, and the molecular ions , , , and have been created this way.
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Limescale build-up inside a pipe reduces both liquid flow and thermal conduction from the pipe, so will reduce thermal efficiency when used as a heat exchanger. A descaling agent or chemical descaler is a liquid chemical substance used to remove limescale from metal surfaces in contact with hot water, such as in boilers, water heaters, and kettles. Limescale is either white or brown in colour due to the presence of iron compounds. Glass surfaces may also exhibit scaling stains, as can many ceramic surfaces present in bathrooms and kitchen, and descaling agents can be used safely to remove those stains without affecting the substrate since both ceramics and glass are unreactive to most acids.
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Sodium sulfate is a typical electrostatically bonded ionic sulfate. The existence of free sulfate ions in solution is indicated by the easy formation of insoluble sulfates when these solutions are treated with Ba2+ or Pb2+ salts: : Na2SO4 \+ BaCl2 → 2 NaCl + BaSO4 Sodium sulfate is unreactive toward most oxidizing or reducing agents. At high temperatures, it can be converted to sodium sulfide by carbothermal reduction (high temperature heating with charcoal, etc.): : Na2SO4 \+ 2 C → Na2S + 2 CO2 This reaction was employed in the Leblanc process, a defunct industrial route to sodium carbonate. Sodium sulfate reacts with sulfuric acid to give the acid salt sodium bisulfate: : Na2SO4 \+ H2SO4 ⇌ 2 NaHSO4 Sodium sulfate displays a moderate tendency to form double salts.
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The vinylsulfone group reacts with the nucleophilic functional groups of the fibers by Michael addition to form a covalent ether bond: > Reaktion der Vinylsulfon-Verbindungen mit den Hydroxylgruppen der Cellulose > Reaction of vinyl sulfone compounds with hydroxyl groups of cellulose (HO- > CELL) An unfavorable side reaction in the dyeing process is the conversion of the vinylsulfone group to the 2-(hydroxy)ethylsulfonyl group:Die Reaktion der VS- Reaktivfarbstoffe mit Wasser wird in der Literatur auch als "Hydrolyse" bezeichnet, siehe: > Reaktion der Vinylsulfon-Verbindungen mit Wasser/OH− als unerwünschte > Nebenreaktion beim Färben > Reaction of vinylsulfone compounds with water/OH− during dying The hydroxylated, unreactive dye has to be washed out during the post- treatment.
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3 H2O + \underbrace_ This rapid reaction is "chemically analogue" to the slow natural hydration of forsterite (the magnesium end- member of olivine) leading to the formation of serpentine and brucite in nature, although the kinetic of hydration of poorly crystallized artificial belite is much faster than the slow weathering of well crystallized Mg-olivine under natural conditions. \underbrace_ +\underbrace_ -> \underbrace_ + \underbrace_ The hydrate phase, [3 CaO · 2 SiO2 · 3 H2O], is referred to as the "C-S-H" phase. It grows as a mass of interlocking needles that provide the strength of the hydrated cement system. Relatively high belite reactivity is desirable in Portland cement manufacture, and the formation of the unreactive γ-form must be rigorously avoided.
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Iron oxide and cobalt nanoparticles can be loaded onto various surface active materials like alumina to convert gases such as carbon monoxide and hydrogen into liquid hydrocarbon fuels using the Fischer-Tropsch process. Much research on nanomaterial-based catalysts has to do with maximizing the effectiveness of the catalyst coating in fuel cells. Platinum is currently the most common catalyst for this application, however, it is expensive and rare, so a lot of research has been going into maximizing the catalytic properties of other metals by shrinking them to nanoparticles in the hope that someday they will be an efficient and economic alternative to platinum. Gold nanoparticles also exhibit catalytic properties, despite the fact that bulk gold is unreactive.
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Platinum being dissolved in hot aqua regia The most common oxidation states of platinum are +2 and +4. The +1 and +3 oxidation states are less common, and are often stabilized by metal bonding in bimetallic (or polymetallic) species. As is expected, tetracoordinate platinum(II) compounds tend to adopt 16-electron square planar geometries. Although elemental platinum is generally unreactive, it dissolves in hot aqua regia to give aqueous chloroplatinic acid (H2PtCl6): : Pt + 4 HNO3 \+ 6 HCl → H2PtCl6 \+ 4 NO2 \+ 4 H2O As a soft acid, platinum has a great affinity for sulfur, such as on dimethyl sulfoxide (DMSO); numerous DMSO complexes have been reported and care should be taken in the choice of reaction solvent.
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Sarsasapogenin was first isolated in 1914 from Sarsaparilla root. Although it was known to have three oxygen atoms, of which only one is a hydroxyl group, the structure of the side chain remained unclear for many years. Tschesche and Hagedorn proposed an unreactive double tetrahydrofuran structure based on degradation studies which indicated an ether oxygen atom attached to C-16.. The true nature of the side chain – a ketone spiro acetal – was discovered by Russell Marker in 1939, when he succeeded in opening the six-membered pyran ring with acetic anhydride. Marker found that almost the entire side chain could be cleaved in three steps, a process now known as the Marker degradation.
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However, the results of the DECRA trial have been rejected or at least questioned by many practicing neurosurgeons, and a concurrently published editorial raises several study weaknesses. First, the threshold for defining increased ICP, and the time allowed before declaring ICP medically refractory, are not what many practicing physicians would consider increased or refractory. Second, out of almost 3500 potentially eligible patients, only 155 patients were enrolled, showing that the study cannot be generalized to all patients with severe non-penetrating brain injury. Lastly, despite being randomized, more patients in the craniectomy arm had unreactive pupils (after randomization but before surgery) than patients in the medical therapy arm, a potential confounding factor.
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Noble gases are typically highly unreactive except when under particular extreme conditions. The inertness of noble gases makes them very suitable in applications where reactions are not wanted. For example, argon is used in incandescent lamps to prevent the hot tungsten filament from oxidizing; also, helium is used in breathing gas by deep-sea divers to prevent oxygen, nitrogen and carbon dioxide (hypercapnia) toxicity. The properties of the noble gases can be well explained by modern theories of atomic structure: their outer shell of valence electrons is considered to be "full", giving them little tendency to participate in chemical reactions, and it has been possible to prepare only a few hundred noble gas compounds.
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In 1879, the French chemist Édouard Grimaux synthesized barbituric acid from malonic acid, urea, and phosphorus oxychloride (POCl3).Grimaux, Edouard (1879) "Synthèse des dérivés uriques de la série de l'alloxane" (Synthesis of uric derivatives of the alloxan series), Bulletin de la Société chimique de Paris, 2nd series, 31: 146–149. Malonic acid has since been replaced by diethyl malonate,Michael, Arthur (1887) "Ueber neue Reactionen mit Natriumacetessig- und Natriummalonsäureäthern" (On new reactions with sodium acetoacetic- and sodium malonic acid esters), Journal für Praktische Chemie, 2nd series, 35: 449-459; p. 456. because using the ester avoids the problem of having to deal with the acidity of the carboxylic acid and its unreactive carboxylate.
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An elegant demonstration of the power of asymmetric organocatalytic aldol reactions was disclosed by MacMillan and coworkers in 2004 in their synthesis of differentially protected carbohydrates. While traditional synthetic methods accomplish the synthesis of hexoses using variations of iterative protection-deprotection strategies, requiring 8–14 steps, organocatalysis can access many of the same substrates using an efficient two-step protocol involving the proline-catalyzed dimerization of alpha-oxyaldehydes followed by tandem Mukaiyama aldol cyclization. center The aldol dimerization of alpha-oxyaldehydes requires that the aldol adduct, itself an aldehyde, be inert to further aldol reactions. Earlier studies revealed that aldehydes bearing alpha-alkyloxy or alpha- silyloxy substituents were suitable for this reaction, while aldehydes bearing Electron-withdrawing groups such as acetoxy were unreactive.
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This photoredox transformation was shown to be mechanistically distinct from another organocatalytic radical process termed singly-occupied molecular orbital (SOMO) catalysis. SOMO catalysis employs superstoichiometric ceric ammonium nitrate (CAN) to oxidize the catalytically-generated enamine to the corresponding radical cation, which can then add to a suitable coupling partner such as allyl silane. This type of mechanism is excluded for the photocatalytic alkylation reaction because whereas enamine radical cation was observed to cyclize onto pendant olefins and open cyclopropane radical clocks in SOMO catalysis, these structures were unreactive in the photoredox reaction. Diagram of Enantioselective Alkylation of Aldehydes via the synergistic combination of organo- and photoredox catalysis This transformation include alkylations with other classes of activated alkyl halides of synthetic interest.
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The Suzuki-Miyaura and Negishi cross- coupling reactions were typically performed with Pd(PPh3)4 as catalyst and were mostly limited to aryl bromides and iodides at elevated temperatures, while the widely available aryl chlorides were unreactive. The development of new classes of ligands was needed to address these limitations. Since this initial report, extensive work has been done by the Buchwald and Hartwig groups, among other laboratories, to develop sterically-hindered and electron- rich phosphine ligands to enable the catalysis of wide range of reactions including the Buchwald-Hartwig amination and etherification reactions, Negishi cross-coupling, and Suzuki-Miyaura cross-coupling. In particular, Buchwald's group focused on the development of the dialkylbiaryl phosphine ligands, while Hartwig's group investigated bisphosphinoferrocene and trialkylphosphine ligands.
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The water vapor with condensed droplets often seen billowing from power stations is created by the cooling systems (not directly from the closed-loop Rankine power cycle). This 'exhaust' heat is represented by the "Qout" flowing out of the lower side of the cycle shown in the T–s diagram below. Cooling towers operate as large heat exchangers by absorbing the latent heat of vaporization of the working fluid and simultaneously evaporating cooling water to the atmosphere. While many substances could be used as the working fluid in the Rankine cycle, water is usually the fluid of choice due to its favorable properties, such as its non-toxic and unreactive chemistry, abundance, and low cost, as well as its thermodynamic properties.
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A strong driving force for the [4+2] cycloaddition of such species is a result of the establishment (or reestablishment) of aromaticity. Common methods for generating o-quinodimethanes include pyrolysis of benzocyclobutenes or the corresponding sulfone, 1,4-elimination of ortho benzylic silanes or stannanes, and reduction of α,α'-ortho benzylic dibromides. in situ generation of o-quinodomethanes On the contrary, stable dienes are rather unreactive and undergo Diels–Alder reactions only at elevated temperatures: for example, naphthalene can function as a diene, leading to adducts only with highly reactive dienophiles, such as N-phenyl- maleimide. Anthracene, being less aromatic (and therefore more reactive for Diels–Alder syntheses) in its central ring can form a 9,10 adduct with maleic anhydride at 80 °C and even with acetylene, a weak dienophile, at 250 °C.
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Silica is converted to silicon by reduction with carbon. Fluorine reacts with silicon dioxide to form SiF4 and O2 whereas the other halogen gases (Cl2, Br2, I2) are essentially unreactive. Silicon dioxide is attacked by hydrofluoric acid (HF) to produce hexafluorosilicic acid: :SiO2 + 6 HF -> H2SiF6 + 2 H2O HF is used to remove or pattern silicon dioxide in the semiconductor industry. Under normal conditions, silicon does not react with most acids but is dissolved by hydrofluoric acid. :Si(s) + 6HF(aq) -> [SiF6]^{2-}(aq) + 2H+(aq) + 2H2(g) Silicon is attacked by bases such as aqueous sodium hydroxide to give silicates. :Si(s) + 4NaOH(aq) -> [SiO4]^{4-}(aq) + 4Na+(aq) + 2H2(g) Silicon dioxide acts as a Lux–Flood acid, being able to react with bases under certain conditions.
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Rotary lime kiln (rust-colored horizontal tube at right) with preheater, Wyoming, 2010 Traditional lime kiln in Sri Lanka A lime kiln is a kiln used for the calcination of limestone (calcium carbonate) to produce the form of lime called quicklime (calcium oxide). The chemical equation for this reaction is :CaCO3 \+ heat → CaO + CO2 This reaction takes place at (at which temperature the partial pressure of CO2 is 1 atmosphere), but a temperature around 1000 °C (1800 °F; at which temperature the partial pressure of CO2 is 3.8 atmospheresCRC Handbook of Chemistry and Physics, 54th Ed, p F-76) is usually used to make the reaction proceed quickly.Parkes, G.D. and Mellor, J.W. (1939). Mellor's Modern Inorganic Chemistry London: Longmans, Green and Co. Excessive temperature is avoided because it produces unreactive, "dead- burned" lime.
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Scientists were unable to prepare compounds of argon until the end of the 20th century, but these attempts helped to develop new theories of atomic structure. Learning from these experiments, Danish physicist Niels Bohr proposed in 1913 that the electrons in atoms are arranged in shells surrounding the nucleus, and that for all noble gases except helium the outermost shell always contains eight electrons. In 1916, Gilbert N. Lewis formulated the octet rule, which concluded an octet of electrons in the outer shell was the most stable arrangement for any atom; this arrangement caused them to be unreactive with other elements since they did not require any more electrons to complete their outer shell. In 1962, Neil Bartlett discovered the first chemical compound of a noble gas, xenon hexafluoroplatinate.
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Fluorine 3D molecule The bond energy of difluorine is much lower than that of either or and similar to the easily cleaved peroxide bond; this, along with high electronegativity, accounts for fluorine's easy dissociation, high reactivity, and strong bonds to non-fluorine atoms. Conversely, bonds to other atoms are very strong because of fluorine's high electronegativity. Unreactive substances like powdered steel, glass fragments, and asbestos fibers react quickly with cold fluorine gas; wood and water spontaneously combust under a fluorine jet.. Reactions of elemental fluorine with metals require varying conditions. Alkali metals cause explosions and alkaline earth metals display vigorous activity in bulk; to prevent passivation from the formation of metal fluoride layers, most other metals such as aluminium and iron must be powdered, and noble metals require pure fluorine gas at 300–450 °C (575–850 °F).
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Mechanism of peptide bond cleavage in α-chymotrypsin Chymotrypsin cleaves peptide bonds by attacking the unreactive carbonyl group with a powerful nucleophile, the serine 195 residue located in the active site of the enzyme, which briefly becomes covalently bonded to the substrate, forming an enzyme-substrate intermediate. Along with histidine 57 and aspartic acid 102, this serine residue constitutes the catalytic triad of the active site. These findings rely on inhibition assays and the study of the kinetics of cleavage of the aforementioned substrate, exploiting the fact that the enzyme-substrate intermediate p-nitrophenolate has a yellow colour, enabling measurement of its concentration by measuring light absorbance at 410 nm. The reaction of chymotrypsin with its substrate was found to take place in two stages, an initial “burst” phase at the beginning of the reaction and a steady-state phase following Michaelis-Menten kinetics.
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CFC-113 is a very unreactive chlorofluorocarbon. It remains in the atmosphere about 90 years, sufficiently long that it will cycle out of the troposphere and into the stratosphere. In the stratosphere, CFC-113 can be broken up by ultraviolet radiation (where sunlight in the 190-225 nm (UV) range), generating chlorine radicals (Cl•), which initiate degradation of ozone requiring only a few minutes: :CFCl → CFCl + Cl• :Cl• + O → ClO• + O This reaction is followed by: :ClO• + O → Cl• + O The process regenerates Cl• to destroy more O. The Cl• will destroy an average of 100,000 O molecules during its atmospheric lifetime of 1–2 years. In some parts of the world, these reactions have significantly thinned the Earth's natural stratospheric ozone layer that shields the biosphere against solar UV radiation; increased UV levels at the surface can cause skin cancer or even blindness.
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The initial aqueous solution contains hydrogen peroxide, an iodate, divalent manganese (Mn2+) as catalyst, a strong chemically unreactive acid (sulphuric acid (H2SO4) or perchloric acid (HClO4) are good), and an organic compound with an active ("enolic") hydrogen atom attached to carbon which will slowly reduce free iodine (I2) to iodide (I−). (Malonic acid (CH2(COOH)2) is excellent for that purpose.) Starch is optionally added as an indicator to show the abrupt increase in iodide ion concentration as a sudden change from amber (free iodine) to dark blue (the "iodine-starch complex", which requires both iodine and iodide.) Recently it has been shown, however, that the starch is not only an indicator for iodine in the reaction. In the presence of starch the number of oscillations is higher and the period times are longer compared to the starch-free mixtures. It was also found that the iodine consumption segment within one period of oscillation is also significantly longer in the starch-containing mixtures.
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A Sandwich compound with two Cyclooctatetraene ligands Actinides form sandwich complexes with cyclooctatetraene analogously to how transition metals react with cyclopentadienyl ligands. Actinide ions have atomic radii that are too large to form MCp2 compounds, so that they prefer to react with C8H82- ions instead. The first example of this type of chemical species was discovered in 1968 by Andrew Streitwieser, who prepared uranocene by reacting K(COT)2 with UCl4 in tetrahydrofuran at 0 °C. The compounds itself is a pyrophoric green solid that is otherwise quite unreactive. The original synthesis of uranocene Most tetravalent actinides react similarly to form actinocenes: Bis(cyclooctatetraene)protactinium was first prepared in 1973 by turning protactinium(V) oxide into the pentachloride and reducing it with aluminium powder before reacting it with potassium cyclooctatetraenide. :Pa2O5 + SOCl2 ->[400C] PaCl5 :3PaCl5 + Al -> 3PaCl4 + AlCl3 :PaCl4 + 2K2(COT) -> Pa(COT)2 + 4KCl: Neptunocene and thorocene were made similarly using the tetrachlorides.
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Peptides are able to perform as excellent building blocks for a wide range of materials as they can be designed to combine with a range of other building blocks such as lipids, sugars, nucleic acids, metallic nanocrystals and so on; this gives the peptides an edge over carbon nanotubes, which are another popular nanomaterial, as the carbon structure is unreactive. They also exhibit properties such as biocompatibility and molecular recognition; the latter is particularly useful as it enables specific selectivity for building ordered nanostructures. Additionally peptides have superb resistance to extreme conditions of high/low temperatures, detergents and denaturants. The ability of peptides to perform self-assembly allows them to be used as fabrication tools, which is currently and will continue to grow as a fundamental part of nanomaterials production. The self-assembling of peptides is facilitated through the molecules’ structural and chemical compatibility with each other, and the structures formed demonstrates physical and chemical stability.
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The reactivity series is sometimes quoted in the strict reverse order of standard electrode potentials, when it is also known as the "electrochemical series": :Li > Cs > Rb > K > Ba > Sr > Na > Ca > Mg > Be > Al > H (in water) > Mn > Zn > Cr(+3) > Fe(+2) > Cd > Co > Ni > Sn > Pb > H (in acids) > Cu > Fe(+3) > Hg > Ag > Pd > Ir > Pt(+2) > Au The positions of lithium and sodium are changed on such a series; gold and platinum are in joint position and not gold leading, although this has little practical significance as both metals are highly unreactive. Standard electrode potentials offer a quantitative measure of the power of a reducing agent, rather than the qualitative considerations of other reactive series. However, they are only valid for standard conditions: in particular, they only apply to reactions in aqueous solution. Even with this proviso, the electrode potentials of lithium and sodium – and hence their positions in the electrochemical series – appear anomalous.
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The molecule is tetrahedral with C2v symmetry. The S-O distance is 140.5 pm, S-F is 153.0 pm. As predicted by VSEPR, the O-S-O angle is more open than the F-S-F angle, 124° and 97°, respectively. One synthesis begins with the preparation of potassium fluorosulfite:Seel, F. "Potassium Fluorosulfite" Inorganic Syntheses 1967, IX, pages 113-115. . :SO2 \+ KF → KSO2F This salt is then chlorinated to give sulfuryl chloride fluoride: :KSO2F + Cl2 → SO2ClF + KCl Further heating at 180 °C of potassium fluorosulfite with the sulfuryl chloride fluoride gives the desired product:Seel, F. "Sulfuryl Chloride Fluoride and Sulfuryl Fluoride" Inorganic Syntheses 1967, vol. IX, pages 111-113. :SO2ClF + KSO2F → SO2F2 \+ KCl + SO2 Heating metal fluorosulfonate salts also gives this molecule: :Ba(OSO2F)2 → BaSO4 \+ SO2F2 It can be prepared by direct reaction of fluorine with sulfur dioxide: :SO2 \+ F2 → SO2F2 On a laboratory scale, sulfuryl fluoride has been conveniently prepared from 1,1'-sulfonyldiimidazole, in the presence of potassium fluoride and acid. Sulfuryl fluoride is unreactive toward molten sodium metal.
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