56 Sentences With "isolable" | Random Sentence Generator

That's the idea that what matters to human health is not food per se but rather a handful of isolable biochemical factors.

Following the essay on Darwin's overlooked late writing is one about Freud's early work as a neurologist, and how those 20 years of research led him to arrive, by the 1890s, at a vision of the brain as dynamic, its functions not located in isolable centers, but rather achieved through complex systems, open to modification through experience and learning.

The compound forms an isolable ozonide, which degrades above 0 °C to release singlet O2.

Synthesis of an isolable silylene. The α-amido centers stabilize silylenes by п-donation. The dehalogenation of diorganosilicon dihalides is a widely exploited.

Some metal complexes exhibit catalytic properties. The compound H(CHB11Cl11) is a superacid, forming an isolable salt with protonated benzene, C6H. It protonates fullerene, C60.

It is unstable under normal laboratory conditions, but the hydrochloride [CH3C(O)CH2NH3]Cl is readily isolable. Aminoacetone is derived from decarboxylation of alanine. Aminoacetaldehyde is produced by the hydroxylation of taurine.

Recently, a new computational study has showed that most hypervalent halogen hydrides HalHn can exist. It is suggested that IH3 and IH5 are stable enough to be observable or, possibly, even isolable.

Other similar lists have since been made. It influenced Christina Stead and George Pierce Baker, the author of Dramatic Technique. The situations have been critiqued as being "concatenations of events rather than minimal or isolable motifs".

Structure of the hexathionate dianion. Polythionates are oxoanions with the formula Sn(SO3)22- (n≥0). They occur naturally and are the products of redox reactions of thiosulfate. Polythionates are readily isolable, unlike the parent polythionic acids.

Other examples include 2-hydroxytetrahydrothiophene and the anti-HIV drug Lamivudine. Another class of isolable hemithioacetals are derived from carbonyl groups that form stable hydrates. For example, thiols react with hexafluoroacetone trihydrate to give hemithioacetals, which can be isolated.

Chromate esters of allyl alcohols may isomerize via formal [3,3]-sigmatropic shift to give rearranged enone products. An example of an isolable chromate ester is ((CH3)3CO)2CrO2.Fillmore Freeman, "Di-tert-butyl Chromate" Encyclopedia of Reagents for Organic Synthesis, 2001, John Wiley & Sons, Ltd.

The acidity of was found to vastly exceed that of triflic acid, , and bistriflimide, , compounds previously regarded as the strongest isolable acids. Their high acidities stem from the extensive delocalization of their conjugate bases, carboranate anions (CXB11Y5Z6–), which are usually further stabilized by electronegative groups like Cl, F, and CF3. Due to the lack of oxidizing properties and the exceptionally low nucleophilicity and high stability of their conjugate bases, they are the only superacids known to protonate C60 fullerene without decomposing it. Additionally, they form stable, isolable salts with protonated benzene, C6H7+, the parent compound of the Wheland intermediates encountered in electrophilic aromatic substitution reactions.

Hexafluorophosphoric acid is the inorganic compound with the chemical formula (also written ). This strong Brønsted acid features a non-coordinating anion, hexafluorophosphate (). It is formed from the reaction of hydrogen fluoride with phosphorus pentafluoride. Like many strong acids, hexafluorophosphoric acid is not isolable but is handled only in solution.

Tropylium tetrafluoroborate is an organic compound with the formula C7H7BF4. Containing the tropylium cation and the non-coordinating tetrafluoroborate counteranion, tropylium tetrafluoroborate is a rare example of a readily isolable carbocation. It is a white solid. This compound may be prepared by the reaction of cycloheptatriene with phosphorus trichloride, followed by tetrafluoroboric acid.

Stable, isolable, diradicals include singlet oxygen and triplet oxygen. Other important diradicals are certain carbenes and nitrenes. Lesser known diradicals are nitrenium ions, carbon chains and organic so-called non- Kekulé molecules in which the electrons reside on different carbon atoms. In inorganic chemistry, the concept of diradical is not applied although many metal complexes have triplet ground states.

Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH3CO)2O. Commonly abbreviated Ac2O, it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a colorless liquid that smells strongly of acetic acid, which is formed by its reaction with moisture in the air.

Vanadium hexacarbonyl is the inorganic compound with the formula V(CO)6. It is a blue-black volatile solid. This highly reactive species is noteworthy from theoretical perspectives as a rare isolable homoleptic metal carbonyl that is paramagnetic. Most species with the formula Mx(CO)y follow the 18-electron rule, whereas V(CO)6 has 17 valence electrons.

Chlorous acid is a powerful oxidizing agent, although its tendency to disproportionation counteracts its oxidizing potential. Chlorine is the only halogen to form an isolable acid of formula HXO2.Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier Neither bromous acid nor iodous acid has ever been isolated. A few salts of bromous acid, bromites, are known, but no iodites.

Classically, aromatization reactions involve changing the C:H ratio of a substrate. When applied to cyclopentadiene, proton removal gives the aromatic conjugate base cyclopentadienyl anion, isolable as sodium cyclopentadienide: :2 Na + 2 C5H6 -> 2 NaC5H5 \+ H2 Aromatization can entail removal of hydride. Tropylium, arises by the aromatization reaction of cycloheptatriene with hydride acceptors. : + → + + Ciamician-Dennstedt rearrangement of a pyrrole to a pyridine.

Dinitrogen trioxide is the chemical compound with the formula N2O3. This deep blue solid is one of the simple nitrogen oxides. It forms upon mixing equal parts of nitric oxide and nitrogen dioxide and cooling the mixture below −21 °C (−6 °F): :NO + NO2 N2O3 Dinitrogen trioxide is only isolable at low temperatures, i.e. in the liquid and solid phases.

The spin states of these complexes are sensitive to the nature of the amine substituents. Iron tris(dithiocarbamate)s characteristically react with nitric oxide to give Fe(dtc)2NO. This efficient chemical trapping reaction provides a means to detect NO. Reflecting the strongly donating properties of dithiocarbamate ligands, iron tris(dithiocarbamate)s oxidize at relatively mild potentials to give isolable iron(IV) derivatives [Fe(S2CNR2)3]+.

2-Hydroxytetrahydrothiophene is a rare example of a hemithioacetal that can be isolated. Hemithioacetals ordinarily readily dissociate into thiol and aldehyde, however some have been isolated. In general these isolable hemithioacetals are cyclic, which disfavors dissociation, and can often be further stabilized by the presence of acid. An important class are S-glycosides, such as octylthioglucoside, which are formed by a reaction between thiols and sugars.

The para-nitrobenzoate, bistriflimide, and certain nitrile complexes represent catalytically active yet isolable silver-free precatalysts. Cationic gold(I) forms π-complexes with alkene or alkyne bonds, following the Dewar–Chatt–Duncanson model. Gold is certainly not the only metal showing this type of bonding and reactivity, several metal ions isolobal with the simple proton (i.e., an empty s-orbital) do as well: for example, mercury(II) and platinum(II).

Because of their reactivity and instability, alkanesulfinyl chlorides are generally used without purification immediately after their synthesis. Storage is not recommended since pressure develops within the container due to hydrogen chloride release. Treatment of alkanesulfinyl chlorides having α-hydrogens with tertiary amine bases gives thiocarbonyl S-oxides (sulfines) as isolable compounds. Thus, treatment of n-propanesulfinyl chloride with triethylamine gives syn-propanethial-S-oxide, the lachrymatory agent of the onion.

Chiral boronate Lewis acid derived from (1R)-(+)-camphor form a frustrated Lewis pair with tBu3P, which is isolable as a salt. This FLP catalyses the enantioselective hydrogenation of some aryl imines in high yield but modest ee (up to 83%). center Although conceptually interesting, the protocol suffers from lack of generality. It was found that increasing steric bulk of the imine substituents lead to decreased yield and ee of the amine product.

The acidic properties of the As–H bond are often exploited. Thus, AsH3 can be deprotonated: ::AsH3 \+ NaNH2 → NaAsH2 \+ NH3 Upon reaction with the aluminium trialkyls, AsH3 gives the trimeric [R2AlAsH2]3, where R = (CH3)3C. This reaction is relevant to the mechanism by which GaAs forms from AsH3 (see below). AsH3 is generally considered non-basic, but it can be protonated by superacids to give isolable salts of the tetrahedral species [AsH4]+.

Simple tetraalkyltitanium compounds however are not typically isolable, owing to the large size of titanium and the electron-deficient nature of its tetrahedral complexes. More abundant and more useful than the simple tetraalkyl compounds are mixed ligand complexes with alkoxide and cyclopentadienyl coligands. Titanium is capable of forming complexes with high coordination numbers. In terms of oxidation states, most organotitanium chemistry, in solution at least, focuses on derivatives of Ti(IV) and Ti(III).

Codorphone synthesis: Exposure of thebaine (1) to mild acid leads to hydrolysis of the enol ether function followed by migration of the double bond to yield the conjugated enone (2). Addition of lithium diethylcuprate proceeds by 1,4-addition from the less hindered side to give the intermediate 3. Treatment of that with cyanogen bromide under von Braun reaction conditions leads to the isolable aminocyanide. This is the converted to the secondary amine (4) by treatment with aqueous base.

As constituent elements, they did not contradict the chemistry of displacement but transcended it: the chemist could never isolate or characterize an element as he characterized a body; an element was not isolable, for it could not be separated from a mixt without re-creating a new mixt in the process. In his book The Sceptical Chymist of 1661, Robert Boyle criticized the traditional understanding of the composition of materials and initiated the modern understanding of chemical elements.

Vanadocene dichloride, the first organovanadium complexes to be reported, is prepared from sodium cyclopentadienyl and vanadium tetrachloride: :2 NaC5H5 \+ VCl4 → VCp2Cl2 \+ 2NaCl Reduction of this compound gives the parent vanadocene (Cp)2V: :VCp2Cl2 \+ LiAlH4 → V(Cp)2 Cp2V2(CO)5 featuring a pair of semi-bridging CO ligands. Vanadocene is the lightest transition metal metallocene that is isolable at room temperature. Vanadocene reacts with high pressures of carbon monoxide to give CpV(CO)4. Photolysis of the tetracarbonyl gives Cp2V2(CO)5.

The radiation from curium is so strong that the metal glows purple in the dark. Curium is one of the most radioactive isolable elements. Its two most common isotopes 242Cm and 244Cm are strong alpha emitters (energy 6 MeV); they have relatively short half-lives of 162.8 days and 18.1 years, and produce as much as 120 W/g and 3 W/g of thermal energy, respectively.Binder, Harry H.: Lexikon der chemischen Elemente, S. Hirzel Verlag, Stuttgart 1999, , pp. 174–178.

The first isolable trisilaallene compound was reported by Kira et al. in 2003, synthesized by reductive dehalogenation of tetrachlorosilane using potassium graphite. This tetraalkyl-substituted trisilallene showed thermal stability up to its melting point around 200 ºC, but decomposed in contact with air. Its remarkable stability is attributable to bulky substituents providing kinetic protection at the terminal silicon atoms. The 29Si-NMR shifts of the central silicon and terminal silicon atoms were observed at 157.0 ppm and 196.9 ppm respectively.

Structure of tetramesityl disilene. Disilenes bearing sterically bulky substituents are isolable and have been well characterized although they remain mainly of academic interest. The first stabilised disilene was tetramesityldisilene, (C6Me3H2)4Si2. The Si=Si distance in this molecule is 2.15 Å, about 10% shorter than a typical Si–Si single bond. The Si2C4 core is roughly planar. Such species are typically prepared by reduction of organosilicon halides: 2 R2SiCl2 \+ 4 Na → R2Si=SiR2 \+ 4 NaCl An alternative synthesis involves photolysis of trisilacyclopropanes.

Cyclooctyne, the smallest isolable cycloalkyne, is able to undergo azide-alkyne Huisgen cycloaddition under mild, physiological conditions in the absence of a copper(I) catalyst due to strain. This reaction has found widespread application as a bioorthogonal transformation for live cell imaging. Although the mild, copper-catalyzed variant of the reaction, CuAAC (copper-catalyzed azide–alkyne cycloaddition) with linear alkynes had been known, development of the copper-free reaction was significant in that it provided facile reactivity while eliminating the need for a toxic metal catalyst.

Peroxymonophosphoric acid is used in organic synthesis as an electrophilic reagent for the oxidation of alkenes, alkynes, aromatic compounds and amines. Due to the strongly acidic nature, only relatively acid-stable epoxides can be prepared from alkenes, for example trans-stilbene oxide from trans-stilbene. Less stable epoxides are cleaved or react further; cyclohexene, styrene or α-methylstyrene yield no isolable epoxides. In the cases of styrene and α-methylstyrene, acid-catalyzed alkyl migrations lead instead to the main products phenylacetic acid and 2-phenylpropionic acid, respectively.

In the latter case, it significantly increases the acidity of a molecule: the anion formed after giving the proton off becomes stable as a result. Consider acetic acid and its mono-, di-, and trifluoroacetic derivatives and their pKa values (4.74, 2.66, 1.24, and 0.23); in other words, the trifluoro derative is 33,800 times stronger an acid than acetic. Fluorine is a principal component of the strongest known charge-neutral acid, . There is evidence for an even stronger acid, , but it has not proved isolable.

It reacts with strong Lewis acids to form salts of the KrF+ and Kr cations. The atomization energy of KrF2 (KrF2(g) → Kr(g) \+ 2F(g)) is 21.9 kcal/mol, giving an average Kr–F bond energy of only 11 kcal/mol,The values of De(F–KrF) and De(F–Kr•) are estimated to be comparable, at ~10-12 kcal/mol, while ΔH(KrF+ → Kr+ \+ F•) is estimated to be ~42 kcal/mol. the weakest of any isolable fluoride. In comparison, difluorine is held together by a bond of 36 kcal/mol.

The reagent competes with the carbonyl for the reactive intermediate, rapidly sequestering [CF3]− in a reversibly-generated -ate complex [(CF3)2Si(CH3)3]−. This -ate complex is unable to react directly with the carbonyl, resulting in powerful inhibition of the chain reaction by the reagent. This inhibitory process is common to all anion-initiated reactions of the reagent, with the identity of the counter- cation (M+) playing a major role in controlling the overall rate. The reagent has largely supplanted trifluoromethyllithium, which is not isolable and rapidly decomposes to yield lithium fluoride and difluorocarbene.

300x300px Due to the facile elimination of N2, most isodiazenes can only be isolated in a matrix at cryogenic temperatures. A small number of highly hindered derivatives with tertiary R groups (e.g., R1= R2 = t-Bu, stable at –127 °C, decomposes at –90 °C; R1—R2 = C(CH3)2CH2CH2CH2(CH3)2C, stable up to –78 °C) are isolable by preparation and chromatography or filtration at low temperature as red solutions. Isodiazenes have been observed to serve as ligands in transition metals complexes, including those of molybdenum and vanadium.

The sole isolable example of a triboracyclopropenyl anion that persists in solution and in the solid state was identified by Braunschweig and coworkers, who synthesized it by reducing the aminoborane Cl2B=NCy2 (Cy = cyclohexyl) with finely dispersed sodium metal in dimethoxyethane (DME). Cooling of the resulting orange-red solution of the dimeric species Na4[B3(NCy2)3]2 • 2 DME resulted in crystals suitable for X-ray diffraction, by which the structure was determined. Although the detailed reduction mechanism is unknown, it has been suggested that subvalent "R2N−B" intermediates are involved in the formation of such boron clusters.

The Roman property law was based on such a corporate system. In a well-known paper that contributed to the creation of the field of law and economics in the late 1960s, the American scholar Harold Demsetz described how the concept of property rights makes social interactions easier: Different societies may have different theories of property for differing types of ownership. Pauline Peters argued that property systems are not isolable from the social fabric, and notions of property may not be stated as such, but instead may be framed in negative terms: for example the taboo system among Polynesian peoples.

Richard Willstätter's original synthesis (4 consecutive elimination reactions on a cyclooctane framework) gives relatively low yields. Reppe's synthesis of cyclooctatetraene, which involves treating acetylene at high pressure with a warm mixture of nickel cyanide and calcium carbide, was much better, with chemical yields near 90%: :Reppe's synthesis of cyclooctatetraene COT can also be prepared by photolysis of barrelene, one of its structural isomers, the reaction proceeding via another isolable isomer, semibullvalene. COT derivatives can also be synthesised by way of semibullvalene intermediates. In the sequence illustrated below, octaethylcyclooctatetraene (C8Et8) is formed by thermal isomerisation of octaethylsemibullvalene, itself formed by copper(I) bromide mediated cyclodimerisation of 1,2,3,4-tetraethyl-1,4-dilithio-1,3-butadiene.

The prototypical super leaving group is triflate, and the term has come to mean any leaving group of comparable ability. Compounds where loss of a super leaving group can generate a stable carbocation are usually highly reactive and unstable. Thus, the most commonly encountered organic triflates are methyl triflate and alkenyl or aryl triflates, all of which cannot form stable carbocations on ionization, rendering them relatively stable. It has been noted that steroidal alkyl nonaflates (another super leaving group) generated from alcohols and perfluorobutanesulfonyl fluoride were not isolable as such but immediately formed the products of either elimination or substitution by fluoride generated by the reagent.

The Büchner–Curtius–Schlotterbeck reaction used in the formation of β-keto esters The Büchner–Curtius–Schlotterbeck reaction can also be used to insert a methylene bridge between a carbonyl carbon and a halogen of an acyl halide. This reaction allows conservation of the carbonyl and halide functionalities. The Büchner–Curtius–Schlotterbeck reaction used to insert a methylene bridge between a halogen and a cabonyl carbon of an acyl halide It is possible to isolate nitrogen-containing compounds using the Büchner–Curtius–Schlotterbeck reaction. For example, an acyl-diazomethane can react with an aldehyde in the presence of a DBU catalyst to form isolable α-diazo-β-hydroxy esters (shown below).

Angle strain in cycloalkynes arises from the deformation of the R–C≡C bond angle which must occur in order to accommodate the molecular geometry of rings containing less than ten carbons. The strain energies associated with cyclononyne (C9H14) and cyclooctyne (C8H12) are approximately 2.9 kcal/mol and 10 kcal/mol, respectively. This upwards trend in energy for the isolable constituents of this class is indicative of a rapid escalation of angle strain with an inverse correlation to ring size. Analysis by photoelectron spectroscopy has indicated that the alkyne bond in small cyclic systems is composed of two non-degenerate π bonds – a highly reactive strained bond perpendicular to a lower-energy π bond.

The rapid growth of organometallic chemistry in the 20th century can be traced to the discovery of ferrocene, a very stable compound which foreshadowed the synthesis of many related sandwich compounds. Ferrocene is formed by reaction of sodium cyclopentadienide with iron(II) chloride: :2 NaC5H5 \+ FeCl2 → Fe(C5H5)2 \+ 2 NaCl Ferrocene displays diverse reactivity localized on the cyclopentadienyl ligands, including Friedel–Crafts reactions and lithation. Some electrophilic functionalization reactions, however, proceed via initial attack at the Fe center to give the bent [Cp2Fe–Z]+ species (which are formally Fe(IV)). For instance, HF:PF5 and Hg(OTFA)2, give isolable or spectroscopically observable complexes [Cp2Fe–H]+PF6– and Cp2Fe+–Hg–(OTFA)2, respectively.

Many of the key psychoactive compounds in M. speciosa are indole alkaloids related to mitragynine, which is a tetracyclic relative of the pentacyclic indole alkaloids, yohimbine and voacangine. In particular, mitragynine and 7-hydroxymitragynine (7-HMG) compose significant proportions of the natural products isolable from M. speciosa; e.g., in one study, mitragynine was 12% by weight from Malaysian leaf sources, versus 66% from Thai sources, and 7-hydroxymitragynine constituted ~2% by weight. In addition, at least 40 other compounds have been isolated from M. speciosa leaves, including ~25 additional alkaloids, including raubasine/ajmalicine (originally isolated from Rauvolfia serpentina), corynantheidine (also found in Pausinystalia johimbe), as well as mitraphylline, mitragynine pseudoindoxyl, and rhynchophylline.

As a class, the carborane acids form the most acidic group of well-defined, isolable substances known, far more acidic than previously known single- component strong acids like triflic acid or perchloric acid. In certain cases, like the nearly perhalogenated derivatives mentioned above, their acidities rival (and possibly exceed) those of the traditional mixed Lewis-Brønsted superacids like magic acid and fluoroantimonic acid. (However, a head-to-head comparison has not been possible thus far, due to the lack of a measure of acidity that is suitable for both classes of acids: pKa values are ill-defined for the chemically complex mixed acids while H0 values cannot be measured for the very high melting carborane acids).

Ring size determines the stability of simple cycloalkynes Due to the significant geometric constraints imposed by the R–C≡C–R functionality, cycloalkynes smaller than cyclodecyne (C10H16) result in highly strained structures. While the cyclononyne (C9H14) and cyclooctyne (C8H12) are isolable (though strongly reactive) compounds, cycloheptyne (C7H10), cyclohexyne (C6H8) and cyclopentyne (C5H6) only exist as transient reaction intermediates or as ligands coordinating to a metal center. There is little experimental evidence supporting the existence of cyclobutyne (C4H4) or cyclopropyne (C3H2), aside from studies reporting the isolation of an osmium complex with cyclobutyne ligands. Initial studies which demonstrated the transient intermediacy of the seven-, six- and five-membered cycloalkynes relied on trapping of the high-energy alkyne with a suitable reaction partner, such as a cyclic dienes or diazo compounds to generate the Diels–Alder or diazoalkane 1,3-dipolar cycloaddition products, respectively.

There are many compelling arguments regarding the prevalence and necessity of hierarchy/modularity in nature . points out that among evolving systems, only those that can manage to obtain and then reuse stable subassemblies (modules) are likely to be able to search through the fitness landscape with a reasonably quick pace; thus, Simon submits that "among possible complex forms, hierarchies are the ones that have the time to evolve." This line of thinking has led to the even stronger claim that although "we do not know what forms of life have evolved on other planets in the universe, ... we can safely assume that 'wherever there is life, it must be hierarchically organized'" . This would be a fortunate state of affairs since the existence of simple and isolable subsystems is thought to be a precondition for successful science .

Having an enantiomer by virtue of an asymmetric carbon atom represents the most common type of central chirality. The other three types of chirality do not involve asymmetric carbon atoms, and even central chirality does not require the center of chirality to be located at a carbon or any other atom. Consequently, while the presence of an asymmetric carbon atom is a convenient characteristic to look for when determining whether a molecule will have an enantiomer, it is neither sufficient nor necessary as a criterion. As a rigorous criterion, a molecule is chiral, and will therefore possess an enantiomer, if and only if it belongs to one of the chiral point groups: Cn, Dn, T, O, and I. However, as a caveat, enantiomers are not necessarily isolable if there is an accessible pathway for racemization at a given temperature and timescale.

The nodal plane of the orbitals, viewed as a ribbon, is a Möbius strip, rather than a cylinder, hence the name. The pattern of orbital energies is given by a rotated Frost circle (with the edge of the polygon on the bottom instead of a vertex), so systems with 4n electrons are aromatic, while those with 4n + 2 electrons are anti-aromatic/non-aromatic. Due to incrementally twisted nature of the orbitals of a Möbius aromatic system, stable Möbius aromatic molecules need to contain at least 8 electrons, although 4 electron Möbius aromatic transition states are well known in the context of the Dewar-Zimmerman framework for pericyclic reactions. Möbius molecular systems were considered in 1964 by Edgar Heilbronner by application of the Hückel method, but the first such isolable compound was not synthesized until 2003 by the group of Rainer Herges.

Coniine is a poisonous chemical compound, an alkaloid present in and isolable from poison hemlock (Conium maculatum), where its presence has been a source of significant economic, medical, and historico-cultural interest; coniine is also produced by the yellow pitcher plant (Sarracenia flava), and fool's parsley (Aethusa cynapium). Its ingestion and extended exposure are toxic to humans and all classes of livestock; its mechanism of poisoning involves disruption of the central nervous system, with death caused by respiratory paralysis. The biosynthesis of coniine contains as its penultimate step the non-enzymatic cyclisation of 5-oxooctylamine to γ-coniceine, a Schiff base differing from coniine only by its carbon-nitrogen double bond in the ring. This pathway results in natural coniine that is a mixture—a racemate—composed of two enantiomers, the stereoisomers (S)-(+)-coniine and (R)-(−)-coniine, depending on the direction taken by the chain that branches from the ring.

Dnr S, daunosamine glycosyltransferase catalyzes the addition of the TDP activated glycoside, L-daunosamine-TDP to ε-rhodomycinone to give rhodomycin D (Figure 2). The release of TDP drives the reaction forward. The enzyme has sequence similarity to glycosyltransferases of the other "unusual sugars" added to Type II PKS aromatic products. left Dnr P, rhodomycin D methylesterase, removes the methyl group added previously by DnrC. It initially served to activate the adjacent methylene bridge, and after that it prevented its carboxyl group from leaving the C-10 carbon (see Fig 2). Had the carboxyl group not been esterified prior to the fourth ring cyclization, its departure as [ CO2 would have been favored by the formation of a bicyclic aromatic system. After C-7 reduction and glycosylation, the C-8 methylene bridge is no longer activated for deprotonation, thereby making aromatization less likely. Note that the non-isolable intermediate, with numbering, is the 3rd molecule in Figure 2.

Silylenes are generally synthesized by thermolysis or photolysis of polysilanes, by silicon atom reactions (insertion, addition or abstraction), by pyrolysis of silanes, or by reduction of 1,1-dihalosilane. It has long been assumed that the conversion of metallic Si to tetravalent silicon compounds proceeds via silylene intermediates: :Si + Cl2 → SiCl2 :SiCl2 \+ Cl2 → SiCl4 Similar considerations apply to the Direct process, i.e. the reaction of methyl chloride and bulk silicon. Early observations of silylenes involved generation of dimethylsilylene by dechlorination of dimethyldichlorosilane: :SiCl2(CH3)2 \+ 2 K → Si(CH3)2 \+ 2 KCl The formation of dimethylsilylene was demonstrated by conducting the dechlorination in the presence of trimethylsilane, the trapped product being pentamethyldisilane: :Si(CH3)2 \+ HSi(CH3)3 → (CH3)2Si(H)-Si(CH3)3 A room-temperature isolable silylene is N,N’-di-tert-butyl-1,3-diaza-2-silacyclopent-4-en-2-ylidene, first described in 1994 by Michael K. Denk et al.

In the analogous selenium system, trifluoroperacetic acid oxidation of selenoethers (R–Se–R) produces selones (R–Se(O)2–R) without the formation of the related selenoxides (R–Se(O)–R) as an isolable product, a reaction which is particularly effective when the R is an aryl group. A general approach to the formation of sulfinyl chlorides (RS(O)Cl) is the reaction of the corresponding thiol with sulfuryl chloride (). In cases where the sulfenyl chloride (RSCl) results instead, a subsequent trifluoroperacetic acid oxidation affords the desired product, as in the case of 2,2,2-trifluoro-1,1-diphenylethanethiol: center The trifluoroperacetic acid oxidation of thiophene illustrates competing pathways for reaction, with both S-oxidation and epoxidation being possible. The major pathway initially forms the sulfoxide, but this chemical promptly undergoes a Diels-Alder-type dimerisation before any further oxidation occurs—neither thiophene-S-oxide or thiophene-S,S-dioxide are found among the products of the reaction.