Solvation significantly affects the basicity of amines. N-H groups strongly interact with water, especially in ammonium ions. Consequently, the basicity of ammonia is enhanced by 1011 by solvation. The intrinsic basicity of amines, i.e.
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This is the same sign convention as is used for electron affinity. The property related to the proton affinity is the gas-phase basicity, which is the negative of the Gibbs energy for above reactions,"Gas-phase basicity." Compendium of Chemical Terminology. i.e. the gas-phase basicity includes entropic terms in contrast to the proton affinity.
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Owing to inductive effects, the basicity of an amine might be expected to increase with the number of alkyl groups on the amine. Correlations are complicated owing to the effects of solvation which are opposite the trends for inductive effects. Solvation effects also dominate the basicity of aromatic amines (anilines). For anilines, the lone pair of electrons on nitrogen delocalises into the ring, resulting in decreased basicity.
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Total soluble alkalinity titrimetric method for the determination of the basicity of soluted material was applied.
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Alkalinity is sometimes incorrectly used interchangeably with basicity. For example, the addition of CO2 lowers the pH of a solution. This increase reduces the basicity; however, the alkalinity remains unchanged (see example below). For total alkalinity testing, 0.1 N H2SO4 is used by hydrologists along with phenolphthalein pH indicator.
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Substituents on the aromatic ring, and their positions relative to the amino group, also affect basicity as seen in the table.
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Relative stabilization of methylammonium ions thus decreases with the number of methyl groups explaining the order of water basicity of methylamines.
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Although phosphinoimidates are formally anions, salts of the anions are typically unavailable owing to their high basicity. Instead the ligand is installed indirectly.
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Due to the high basicity of the fluoride anion, the salt reacts slowly with acetonitrile, inducing its dimerization to CH3C(NH2)=CHCN, which co-crystallizes.
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It is used as the standard Lewis acid in the Gutmann scale of Lewis basicity. However, Cramer-Bopp plots show that a one-parameter basicity scale is incomplete and that there is no single rank order of base strength. These plots show that to define the order of Lewis base strength (or Lewis acid strength) at least two properties must be considered.Laurence, C. and Gal, J.-F.
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The formation of the oxyphosphonium intermediate 8 is slow and facilitated by the alkoxide. Therefore, the overall rate of reaction is controlled by carboxylate basicity and solvation.
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EB and CB parameters for phosphines that can be used in combination with the improved parameters for oxygen, nitrogen, and sulfur donors to measure σ-basicity have been reported.
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Specifically, notable examples include both paper used for the regular purpose of printing, and the more specialized case of litmus paper, which in itself is used to characterize acidity and basicity.
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Perfluorotripentylamine is a perfluorocarbon. It is used as an electronics coolant, and has a high boiling point. It is colorless, odorless, and insoluble in water. Unlike ordinary amines, perfluoroamines are of low basicity.
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The high basicity is attributed to the relief of strain upon protonation and/or the strong interaction between the nitrogen lone pairs. Additionally, although many aromatic amines such as aniline show reduced basicity (due to nitrogen being sp² hybridized; its lone pair occupying a 2p orbital and interacting and being withdrawn by the aromatic ring), this is not possible in this molecule, as the nitrogens' methyl groups prevent its substituents from adopting a planar geometry, as this would require forcing methyl groups from each nitrogen atom into one another - thus the basicity is not reduced by this factor which is found in other molecules. It is sterically hindered, making it a weak nucleophile. Because of this combination of properties, it has been used in organic synthesis as a highly selective non-nucleophilic base.
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Owing to the influence of the nitro substituent, the amine exhibits a basicity nearly 100,000x lower than aniline itself. Diazotization gives diazonium derivative, which is a precursor to some diazo dyes. Acetylation affords 2-nitroacetanilide.
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The selection of a matrix is the first step when preparing samples for MALDI analysis. The primary goals of the matrix are to absorb the energy from a laser, thus transferring it to the analyte molecules, and to separate the analyte molecules from each other. A consideration that should be taken into account when choosing a matrix is what type of analyte ion is expected or desired. Knowing the acidity or basicity of the analyte molecule compared with the acidity or basicity of the matrix, for example, is valuable knowledge when choosing a matrix.
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The inductive effect also plays a vital role in deciding the acidity and basicity of a molecule. Groups having effect (Inductive effect) attached to a molecule increases the overall electron density on the molecule and the molecule is able to donate electrons, making it basic. Similarly, groups having effect attached to a molecule decreases the overall electron density on the molecule making it electron deficient which results in its acidity. As the number of groups attached to a molecule increases, its acidity increases; as the number of groups on a molecule increases, its basicity increases.
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1,8-Bis(dimethylamino)naphthalene is an organic compound with the formula CH(NMe) (Me = methyl). It is classified as a peri-naphthalene, i.e. a 1,8-disubstituted derivative of naphthalene. Owing to its unusual structure, it exhibits exceptional basicity.
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Simplismo is a literary technique that was developed and employed by the Peruvian poet Alberto Hidalgo in the mid-twentieth century. The equivalent of “simplism” in English, it emphasizes basicity in writing and asserts that there is more to be said with less.
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Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters. Improved E&C; parameters are listed in ECW model.
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Some quaternary ammonium salts of naked fluoride include tetramethylammonium fluoride and tetrabutylammonium fluoride. Cobaltocenium fluoride is another example. However, they all lack structural characterization in aprotic solvents. Because of their high basicity, many so- called naked fluoride sources are in fact bifluoride salts.
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They derive their name from the alkali metal group of elements, to which sodium belongs, and which can induce basicity. Sometimes these soils are also referred to as alkaline sodic soils. Alkaline soils are basic, but not all basic soils are alkaline.
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Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters. Improved E&C; parameters are listed in ECW model. .
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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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Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters. Improved E&C; parameters are listed in ECW model.
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200x200px Intracellular pH (pHi) is the measure of the acidity or basicity (i.e., pH) of intracellular fluid. The pHi plays a critical role in membrane transport and other intracellular processes. In an environment with the improper pHi, biological cells may have compromised function.
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Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters. Improved E&C; parameters are listed in ECW model. It is also a strong oxidizing agent.
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Pyrrolidine is a base. Its basicity is typical of other dialkyl amines. Relative to many secondary amines, pyrrolidine is distinctive because of its compactness, a consequence of its cyclic structure. Pyrrolidine is used as a building block in the synthesis of more complex organic compounds.
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Structure of Fe(tert-BuNC)5. Notice that some C-N-C angles strongly deviate from 180°, a characteristic of low-valent isocyanide complexes. Because of their low steric profile and high basicity, isocyanide ligands often install easily, e.g. by treating metal halides with the isocyanide.
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Like water and ammonia, liquid hydrogen fluoride supports an acid-base chemistry. Using a solvent system definition of acidity and basicity, nitric acid functions as a base when it is added to liquid HF. cited in However, hydrogen fluoride is cosmically rare, unlike water, ammonia, and methane.
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The trifluoromethyl group has a significant electronegativity that is often described as being intermediate between the electronegativities of fluorine and chlorine. For this reason, trifluoromethyl-substituted compounds are often strong acids, such as trifluoromethanesulfonic acid and trifluoroacetic acid. Conversely, the trifluoromethyl group lowers the basicity of compounds like trifluoroethanol.
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In comparison to other oxygen-centered oxidants (hypohalites, anions of peroxides) and in line with its low basicity, bromite is a rather weak nucleophile. Rate constants of bromite towards carbocations and acceptor- substituted olefins are by 1–3 orders of magnitude lower than the ones measured with hypobromite.
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The bisulfide anion can accept a proton: Because of its affinity to accept a proton (H+), bisulfide has a basic character. In aqueous solution, it has a corresponding pKa value of 6.9. Its conjugate acid is hydrogen sulfide (). However, bisulfide's basicity stems from its behavior as an Arrhenius base.
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The trichloromethyl group has a significant electronegativity. For this reason, trichloromethyl-substituted acids are often stronger than the original. For example, the acidity constant (pKa) of trichloroacetic acid – is 0.77, whereas that of acetic acid is 4.76. By the same principle, the trichloromethyl group generally lowers the basicity of organic compounds.
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Some non-aqueous solvents can behave as acids. An acidic solvent will increase basicity of substances dissolved in it. For example, the compound CH3COOH is known as acetic acid because of its acidic behaviour in water. However it behaves as a base in liquid hydrogen chloride, a much more acidic solvent.
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Per the classification by Albert six-membered heterocycles can be described as π-deficient. Substitution by electronegative groups or additional nitrogen atoms in the ring significantly increase the π-deficiency. These effects also decrease the basicity. Like pyridines, in pyrimidines the π-electron density is decreased to an even greater extent.
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Because of the decreased basicity compared to pyridine, electrophilic substitution of pyrimidine is less facile. Protonation or alkylation typically takes place at only one of the ring nitrogen atoms. Mono-N-oxidation occurs by reaction with peracids. Electrophilic C-substitution of pyrimidine occurs at the 5-position, the least electron-deficient.
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The pH of a sodium chloride solution remains ≈7 due to the extremely weak basicity of the Cl− ion, which is the conjugate base of the strong acid HCl. In other words, NaCl has no effect on system pH in diluted solutions where the effects of ionic strength and activity coefficients are negligible.
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Second generation proton sponges are known with even higher basicity. 1,8-bis(hexamethyltriaminophosphazenyl)naphthalene or HMPN is prepared from 1,8-diaminonaphthalene by reaction with tris(dimethylamino)bromophosphonium bromide in the presence of triethylamine. HMPN has a pK of 29.9 in acetonitrile which is more than 11 orders of magnitude higher than Proton Sponge.
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Formol titration equation for prolineThere has been some inaccuracies of the SFT caused by the differences in the basicity of the nitrogen in different amino acids which were explained by S. L. Jodidi. For instances, proline(an imino acid), histidine, and lysine yields too low values compared to the theory. Unlike alpha, monobasic (containing one amino group per molecule) amino acids, these amino (or imino) acids' nitrogens have inconstant basicity, which results in partial reaction with formaldehyde.S. L. Jodidi "Abnormalities In the Formol Titration Method" Journal of American Chemical Society 1918 40 (7), 1031-1035 DOI: 10.1021/ja02240a006 In case of tyrosine, the actual results are too high due to the negative hydroxyl group (-OH), which acts as a base.
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The Edwards equation in organic chemistry is a two-parameter equation for correlating nucleophilic reactivity, as defined by relative rate constants, with the basicity of the nucleophile (relative to protons) and its polarizability. This equation was first developed by John O. Edwards in 1954 and later revised based on additional work in 1956. The general idea is that most nucleophiles are also good bases because the concentration of negatively charged electron density that defines a nucleophile will strongly attract positively charged protons, which is the definition of a base according to Brønsted–Lowry acid-base theory. Additionally, highly polarizable nucleophiles will have greater nucleophilic character than suggested by their basicity because their electron density can be shifted with relative ease to concentrate in one area.
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A later paper by Edwards and Pearson, following research done by Jencks and Carriuolo in 1960 led to the discovery of an additional factor in nucleophilic reactivity, which Edwards and Pearson called the alpha effect, where nucleophiles with a lone pair of electrons on an atom adjacent to the nucleophilic center have enhanced reactivity. The alpha effect, basicity, and polarizability are still accepted as the main factors in determining nucleophilic reactivity. As such, the Edwards equation is applied in a qualitative sense much more frequently than in a quantitative one. In studying nucleophilic reactions, Edwards and Pearson noticed that for certain classes of nucleophiles most of the contribution of nucleophilic character originated from their basicity, resulting in large β values.
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Diethylaluminum cyanide is used for the stoichiometric hydrocyanation of α,β-unsaturated ketones. The reaction is influenced by the basicity of the solvent. This effect arises from the Lewis acidic qualities of the reagent. The purpose of this reaction is to generate alkylnitriles, which are precursors to amines, amides, carboxylic acids esters and aldehydes.
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This type of metal-free hydrogenation has the potential to replace high cost metal catalyst. The mechanism of imine reduction is proposed to involve protonation at nitrogen giving the iminium salt. The basicity of the nitrogen centre determines the rate of reaction. More electron rich imines reduce at faster rates than electron poor imines.
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It is one of the strongest amine bases known. The high basicity is attributed to the relief of strain upon protonation and strong internal hydrogen bonding. Effects of the solvent and solvation should be mentioned also in this section. It turns out, these influences are more subtle than that of a dielectric medium mentioned above.
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Ph3PO is a tetrahedral molecule related to POCl3.D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam. . The oxygen center is relatively basic. The rigidity of the backbone and the basicity of the oxygen center make this species a popular agent to crystallize otherwise difficult to crystallize molecules.
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Therefore, electrophilic aromatic substitution is more difficult while nucleophilic aromatic substitution is facilitated. An example of the last reaction type is the displacement of the amino group in 2-aminopyrimidine by chlorine and its reverse. Electron lone pair availability (basicity) is decreased compared to pyridine. Compared to pyridine, N-alkylation and N-oxidation are more difficult.
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Its relative acceptor strength toward a series of bases, versus other Lewis acids, can be illustrated by C-B plots.Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9Cramer, R. E., and Bopp, T. T. (1977) Great E and C plot.
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A compound which is a weak acid in water may become a strong acid in DMSO. Acetic acid is an example of such a substance. An extensive bibliography of pKa values in solution in DMSO and other solvents can be found at Acidity–Basicity Data in Nonaqueous Solvents. Superacids are strong acids even in solvents of low dielectric constant.
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2-Nitroaniline is the main precursor to phenylenediamines, which are converted to benzimidazoles, a family of heterocycles that are key components in pharmaceuticals. Intramolecular hydrogen-bonding results in a very low basicity for 2-nitroaniline. Aside from its reduction to phenylenediamine, 2-nitroaniline undergoes other reactions anticipated for aromatic amines. It is protonated to give the anilinium salts.
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In general, in a group across the periodic table, the more basic the ion (the higher the pKa of the conjugate acid) the more reactive it is as a nucleophile. Within a series of nucleophiles with the same attacking element (e.g. oxygen), the order of nucleophilicity will follow basicity. Sulfur is in general a better nucleophile than oxygen.
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As well as his research science he is a hobby artist, examples of his work can be found on his research page in external links Key works done by Michael Abraham and UCL co-workers include the measuring and calculation of molecular properties of thousands of molecules. These properties include H-bond acidity and basicity, dipolarity and polarisability.
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Organolithium reagents provide a wide range of basicity. tert- Butyllithium, with three weakly electron donating alkyl groups, is the strongest base commercially available (pKa = 53). As a result, the acidic protons on -OH, -NH and -SH are often protected in the presence of organolithium reagents. Some commonly used lithium bases are alkyllithium species such as n-butyllithium and lithium dialkylamides (LiNR2).
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Both amines affect the regiochemistry of metalation. In the PMDTA/n-BuLi adducts, the Li-C bonds are highly polarized, thus increasing the basicity of the butyl group. The effect of PMDTA on lithium anilide is illustrative of PMDTA's complexing power. The complex, [{PhN(H)Li}3·2PMDTA], is trinuclear, featuring approximately colinear Li+ centers that are three-, four-, and five- coordinate.
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Phosphorus trichloride has a lone pair, and therefore can act as a Lewis base, e.g., forming a 1:1 adduct Br3B-PCl3. Metal complexes such as Ni(PCl3)4 are known, again demonstrating the ligand properties of PCl3. This Lewis basicity is exploited in the Kinnear–Perren reaction to prepare alkylphosphonyl dichlorides (RP(O)Cl2) and alkylphosphonate esters (RP(O)(OR')2).
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One of the most characteristic properties of ammonia is its basicity. Ammonia is considered to be a weak base. It combines with acids to form salts; thus with hydrochloric acid it forms ammonium chloride (sal ammoniac); with nitric acid, ammonium nitrate, etc. Perfectly dry ammonia will not combine with perfectly dry hydrogen chloride; moisture is necessary to bring about the reaction.
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Compared to amines, amides are very weak bases. While the conjugate acid of an amine has a pKa of about 9.5, the conjugate acid of an amide has a pKa around −0.5. Therefore, amides don't have as clearly noticeable acid–base properties in water. This relative lack of basicity is explained by the withdrawing of electrons from the amine by the carbonyl.
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These principles can explain the base behavior when they are dissolved in water by recognizing that the oxide ion has a high affinity for protons. Most basic oxides are ionic in nature base on the difference of electronegativity of oxygen and metals. Dissolving basic oxide in water can increase pH (basicity) of water because basic oxides release hydroxide ions (OH−) to the water.
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Metal aromaticity is believed to exist in certain clusters of aluminium, for example. Homoaromaticity is the state of systems where conjugation is interrupted by a single sp hybridized carbon atom. Y-aromaticity is used to describe a Y-shaped, planar (flat) molecule with resonance bonds. The concept was developed to explain the extraordinary stability and high basicity of the guanidinium cation.
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This was explained as being due to the greater relative basicity of the deuterated hydroxide anion compared to the normal hydroxide anion, and was used to indicate that hydrogen migration did not occur in the rate determining step of the reaction. This ruled out a concerted mechanism for the reaction, as hydrogen transfer would occur in the rate determining step.
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Because of its extreme basicity, P4-t-Bu eagerly absorbs water and carbon dioxide, both of which inhibit anionic polymerization. Heating to temperatures >100 °C removes CO2 and water and restores the anionic polymerization. The extreme hygroscopy of the phosphazene base P4-t-Bu as a substance and in solutions requires a great effort for storage and handling and prevents its broader use.
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He pioneered molecular orbital (MO) calculations on σ-bonded polyatomic molecules such as saturated hydrocarbons. He also performed the first MO calculations of the acidity and basicity of aromatic molecules in excited states. He carried out extensive research in molecular spectroscopy. In infrared spectroscopy he studied molecular vibrations as well as overtone bands in hydrogen-bonded systems, and the effect of hydrogen bonds on vibrational anharmonicity.
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This electronic structure leads to a lack of nucleophilicity in general and lack of basicity in particular (pKaH = –14), as well as an ability to form only weak hydrogen bonds. The aqueous solubility of PH3 is slight; 0.22 cm3 of gas dissolves in 1 cm3 of water. Phosphine dissolves more readily in non-polar solvents than in water because of the non-polar P−H bonds.
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Similarly aniline is more basic than ammonia in the gas phase, but ten thousand times less so in aqueous solution. In aprotic polar solvents such as DMSO, DMF, and acetonitrile the energy of solvation is not as high as in protic polar solvents like water and methanol. For this reason, the basicity of amines in these aprotic solvents is almost solely governed by the electronic effects.
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For example, in the presence of concentrated hydrochloric acid at 100 °C, diphenylphosphine adds to the carbon atom in benzaldehyde to give (phenyl-(phenylmethyl)phosphoryl)benzene. :Ph2PH + PhCHO → Ph2P(O)CH2Ph Compared to tertiary phosphines, diphenylphosphine is weakly basic. The pKa of the protonated derivative is 0.03:C. A. Streuli, "Determination of Basicity of Substituted Phosphines by Nonaqueous Titrimetry", Analytical Chemistry 1960, volume 32, pages 985-987.
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The capacity of some compounds to change in function of the pH was known since te sixteenth century. This effect was even known before the discovery of the acidity/basicity concept. Those are found in a wide range of plants like roses, cornflowers, primroses and violets. Robert Boyle was the first person to describe this effect, employing plant juices (in the forms of solution and impregnated paper).
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This type of mixture is called PLX. Other mixtures include ANNM and ANNMAl – explosive mixtures of ammonium nitrate, nitromethane and aluminium powder. As an organic solvent, it is considered to be highly polar (εr = 36 at 20 °C and μ = 3.5 Debye) but is aprotic and possesses very low Lewis basicity. Thus, it is a rare example of a polar solvent that is also weakly coordinating.
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The relative acceptor strength of Lewis acids toward a series of bases, versus other Lewis acids, can be illustrated by C-B plots.Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters. Improved E&C; parameters are listed in ECW model.
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Litmus can also be prepared as an aqueous solution that functions similarly. Under acidic conditions, the solution is red, and under alkaline conditions, the solution is blue. Wet litmus paper can also be used to test for water-soluble gases that affect acidity or basicity; the gas dissolves in the water and the resulting solution colors the litmus paper. For instance, ammonia gas, which is alkaline, turns red litmus paper blue.
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Acyl ligands are intermediates in many carbonylation reactions, which are important in some catalytic reactions. Metal acyls arise usually via insertion of carbon monoxide into metal–alkyl bonds. Metal acyls also arise from reactions involving acyl chlorides with low-valence metal complexes or by the reaction of organolithium compounds with metal carbonyls. Metal acyls are often described by two resonance structures, one of which emphasizes the basicity of the oxygen center.
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Black = no data. Soil pH is a measure of the acidity or basicity (alkalinity) of a soil. pH is defined as the negative logarithm (base 10) of the activity of hydronium ions ( or, more precisely, ) in a solution. In soils, it is measured in a slurry of soil mixed with water (or a salt solution, such as 0.01 M ), and normally falls between 3 and 10, with 7 being neutral.
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Five permanent streams provide 80% of the total influx. The relatively low inflow and high evaporation rates have turned Qinghai saline and alkaline; it is presently about 14 ppt salt with a pH of 9.3. It has increased in salinity and basicity since the early Holocene. At the tip of the peninsula on the western side of the lake are Cormorant Island and Egg Island, collectively known as the Bird Islands.
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The Bird Islands have been sanctuaries of the Qinghai Lake Natural Protection Zone since 1997. There are five native fish species: The edible naked carp (Gymnocypris przewalskii, ), which is the most abundant in the lake, and four stoneloaches (Triplophysa stolickai, T. dorsonotata, T. scleroptera and T. siluroides).. Other Yellow River fish species occurred in the lake, but they disappeared with the increasing salinity and basicity, beginning in the early Holocene.
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Diethyl sulfide is a Lewis base, classified as a soft ligand (see also ECW model).Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by C-B plots.Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters.
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Dimethyl sulfide is a Lewis base, classified as a soft ligand (see also ECW model). Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by C-B plots.Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters.
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Neon has a high first ionization potential of 21.564 eV, which is only exceeded by that of helium (24.587 eV), requiring too much energy to make stable ionic compounds. Neon's polarisability of 0.395 Å3 is the second lowest of any element (only helium's is more extreme). Low polarisability means there will be little tendency to link to other atoms. Neon has a Lewis basicity or proton affinity of 2.06 eV.
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Perfluorotributylamine (PFTBA), also referred to as FC43, is a colorless liquid with the formula N(C4F9)3. The compound consists of three butyl groups connected to an amine center, in which all of the hydrogen atoms have been replaced with fluorine. The compound is produced for the electronics industry, along with other perfluoroalkylamines. The high degree of fluorination significantly reduces the basicity of the central amine due to electron- withdrawing effects.
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It is classified as a hard Lewis base and its ECW model base parameters are EB= 2.19 and CB= 1.31. Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by C-B plots.Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters.
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Aniline is a weak base. Aromatic amines such as aniline are, in general, much weaker bases than aliphatic amines. Aniline reacts with strong acids to form the anilinium (or phenylammonium) ion (C6H5-NH3+). Traditionally, the weak basicity of aniline is attributed to a combination of inductive effect from the more electronegative sp2 carbon and resonance effects, as the lone pair on the nitrogen is partially delocalized into the pi system of the benzene ring.
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This compound is a diamine in which the two dimethylamino groups are attached on the same side (peri position) of a naphthalene ring. This molecule has several very interesting properties; one is its very high basicity; another is its spectroscopic properties. With a pK of 12.34 for its conjugate acid in aqueous solution, 1,8-bis(dimethylamino)naphthalene is one of the strongest organic bases. However, it only absorbs protons slowly—hence the trade name.
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The parent phosphonium is as found in the iodide salt, phosphonium iodide. Salts of the parent are rarely encountered, but this ion is an intermediate in the preparation of the industrially useful tetrakis(hydroxymethyl)phosphonium chloride: :PH3 \+ HCl + 4 CH2O → Many organophosphonium salts are produced by protonation of primary, secondary, and tertiary phosphines: :PR3 \+ H+ → The basicity of phosphines follows the usual trends, with R = alkyl being more basic than R = aryl.
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When acidification occurs, an irreversible conformational change occurs making the final product of an icosahedral capsid. This is done by sending any excess CPs from the RNA to the outside of the new capsid. This process is reliant on the basicity of the CP due to its N-terminal arginine-rich motif (ARM) and the capsid exterior negative charge density. The capsid protein is also involved in viral movement, transmission, symptom expression, and targeted hosts.
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Compared to aniline, the basicity of 2,4-dinitroaniline is even weaker. It is due to the electron-withdrawing nature of the nitro groups. This makes the pKa of conjugate acid of 2,4-dinitroaniline being even lower than that of hydronium ions, meaning that it is a strong acid. :C6H3(NH3+)(NO2)2 + H2O -> C6H3(NH2)(NO2)2 + H3O+ The protons in the amino group is also much more acidic than that of aniline.
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The compound absorbs carbon dioxide (and water vapor) from the air, thus diminishing the alkalinity of the base. :2 + + → 2 + In the solid form, sodium methoxide is polymeric, with sheet-like arrays of Na+ centers, each bonded to four oxygen centers. The structure, and hence the basicity, of sodium methoxide in solution depends on the solvent. It is a significantly stronger base in DMSO where it is more fully ionized and free of hydrogen bonding.
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The triflate ligand is labile, reflecting its low basicity. Trifluoromethanesulfonic acid exothermically reacts with metal carbonates, hydroxides, and oxides. Illustrative is the synthesis of Cu(OTf)2. :CuCO3 \+ 2 CF3SO3H → Cu(O3SCF3)2 \+ H2O + CO2 Chloride ligands can be converted to the corresponding triflates: :3 CF3SO3H + [Co(NH3)5Cl]Cl2 → [Co(NH3)5O3SCF3](O3SCF3)2 \+ 3 HCl This conversion is conducted in neat HOTf at 100 °C, followed by precipitation of the salt upon the addition of ether.
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Solid ionic compounds have long been used as paint pigments, and are resistant to organic solvents, but are sensitive to acidity or basicity. Since 1801 pyrotechnicians have described and widely used metal- containing ionic compounds as sources of colour in fireworks. Under intense heat, the electrons in the metal ions or small molecules can be excited. These electrons later return to lower energy states, and release light with a colour spectrum characteristic of the species present.
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AGH-107 is a potent and selective, water soluble and brain penetrant full agonist at the 5HT7 serotonin receptor. AGH-107 is one of the few examples of low-basicity aminergic receptor agonists, which may underlie its high selectivity over the related central nervous system targets. AGH-107 was found to reverse the impairment in novel object recognition caused by MK-801 in mice. The relatively short half-life in rodents inhibited its use as a molecular probe.
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Sterically hindered metallated compounds, such as n-Butyllithium complexes, are often used as superbases or polymerization initiators because their steric bulk hinders the compound's ability to approach nucleophiles at a distance short enough for nucleophilic attack. Metallated compounds without a high degree of steric bulk, such as methyllithium or alkyl magnesium halides, are more commonly used as nucleophiles or transmetallation reagents — though these compounds' high basicity often requires the protection of basic functional groups found on organic molecules.
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Hydrocyanation is, most fundamentally, the process whereby H+ and -CN ions are added to a molecular substrate. Usually the substrate is an alkene and the product is a nitrile. When -CN is a ligand in a transition metal complex, its basicity makes it difficult to dislodge, so, in this respect, hydrocyanation is remarkable. Since cyanide is both a good σ-donor and π-acceptor its presence accelerates the rate of substitution of ligands trans from itself, the trans effect.
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TBAF can be prepared by passing hydrofluoric acid thorugh an ion-exchange resin, followed by tetrabutylammonium bromide. Upon evaporation of the water, TBAF can be collected as an oil in quantitative yield. Preparing anhydrous samples is of interest as the basicity of fluoride increases by more than 20 pK units on passing from aqueous to aprotic solvent. However, heating samples of the hydrated material to 77 °C under vacuum causes decomposition to the hydrogen difluoride salt.
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The pH is a chemical parameter that measures the acidity or basicity of the water and is commonly measured in situ. Distilled water has a pH of 7, where less than 7 is considered acid and greater than 7 is considered basic. In most cases, low pH is due to organic overloading and low oxygen conditions in the water. This characteristic is strictly controlled because it has a direct effect on water ecosystems and sewer systems materials.
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The group that gave the best effects on basicity was 3-oxo-1,2,4-triazol-5-yl moiety and it gave compounds such as L-741671 and L-742694. A morpholine nucleus that was introduced in L-742694 was found to enhance NK1 binding affinity. This nucleus was preserved in further modifications. In order to prevent possible metabolic deactivation, several refinements such as methylation on the C alfa of the benzyl ring and fluorination on the phenyl ring were introduced.
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Lewis acids have been classified in the ECW model and it has been shown that there is no one order of acid strengths. The relative acceptor strength of Lewis acids toward a series of bases, versus other Lewis acids, can be illustrated by C-B plots.Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters.
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Many modifications have been reported that influence the reactivity of this reagent. The compound adopts a complex cluster structure (the adjacent picture is a simplified cartoon), and additives that modify the cluster affect the reactivity of the reagent. For example, DMF, DMSO, hexamethylphosphoramide (HMPA), and 18-crown-6 interact with the potassium center, enhancing the basicity of the butoxide. Schlosser's base, a mixture of the alkoxide and an alkyl lithium compound, is a related but stronger base.
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Pyridine is a Lewis base, donating its pair of electrons to a Lewis acid. Its Lewis base properties are discussed in the ECW model. Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by C-B plots.Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters.
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Cardo aromatic polyamides have amides incorporated into the backbone, separated by aromatic rings. The aromatic diamines have a low basicity that provides additional challenges to synthesis. Notably, they cannot be synthesized via melt polycondensation. The diamines are not polar enough to dissolve in water, making interfacial polycondensation methods challenging; there has been success from 4’,4” -diphenyl phthalide dicarboxylic chloride and aliphatic diamines as the two phases of the solutions in where the polycondensation can occur at their interface.
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For example, OH− is a better nucleophile than water, and I− is a better nucleophile than Br− (in polar protic solvents). In a polar aprotic solvent, nucleophilicity increases up a column of the periodic table as there is no hydrogen bonding between the solvent and nucleophile; in this case nucleophilicity mirrors basicity. I− would therefore be a weaker nucleophile than Br− because it is a weaker base. Verdict - A strong/anionic nucleophile always favours SN2 manner of nucleophillic substitution.
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This melts the scrap, lowers the carbon content of the molten iron and helps remove unwanted chemical elements. It is this use of pure oxygen (instead of air) that improves upon the Bessemer process, as the nitrogen (an undesirable element) and other gases in air do not react with the charge, and decrease efficiency of furnace.McGannon, p 486 # Fluxes (burnt lime or dolomite) are fed into the vessel to form slag, to maintain basicity above 3 and absorb impurities during the steelmaking process.
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Bis(dicyclohexylphosphino)ethane, abbreviated dcpe, is an organophosphorus compound with the formula (C6H11)2PCH2CH2P(C6H11)2. It is a white solid that is soluble in nonpolar organic solvents. The compound is used as a bulky and highly basic diphosphine ligand in coordination chemistry.Sowa, J. R., Jr., Zanotti, V., Facchin, G., Angelici, R. J., "Calorimetric studies of the heats of protonation of the metal in Fe(CO)3(bidentate phosphine, arsine) complexes: effects of chelate ligands on metal basicity", J. Am. Chem. Soc.
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The loading of trioctylamine for a given carboxylic acid depends on the nature of the solute and its concentration. The apparent extraction equilibrium constants depend on the hydrophobicity and acidity of the carboxylic acid, as well as the specific basicity of trioctylamine. Trioctylamine production can be used as a mineral extraction reagent, an extractant for reactor fuel processing, and its use as an extractant for identification of dyes may result in its release to the environment through various waste streams.
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For the imidazolium halogenoaluminate salts, their physical properties--such as viscosity, melting point, and acidity--could be adjusted by changing the alkyl substituents and the imidazolium/pyridinium and halide/halogenoaluminate ratios. Two major drawbacks for some applications were moisture sensitivity and acidity or basicity. In 1992, Wilkes and Zawarotko obtained ionic liquids with 'neutral' weakly coordinating anions such as hexafluorophosphate () and tetrafluoroborate (), allowing a much wider range of applications. Although many classical ILs are hexafluorophosphate and tetrafluoroborate salts, bistriflimide are also popular.
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Meanwhile, the oxygen atom has lone pairs of nonbonded electrons that render it weakly basic in the presence of strong acids such as sulfuric acid. For example, with methanol: Acidity & basicity of methanol Upon treatment with strong acids, alcohols undergo the E1 elimination reaction to produce alkenes. The reaction, in general, obeys Zaitsev's Rule, which states that the most stable (usually the most substituted) alkene is formed. Tertiary alcohols eliminate easily at just above room temperature, but primary alcohols require a higher temperature.
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Like other alkali metal chalcogenides, this material is highly sensitive to water, easily undergoing hydrolysis to give mixtures of sodium biselenide (NaSeH) and hydroxide. This hydrolysis occurs because of the extreme basicity of the Se2− ion. :Na2Se + H2O → NaHSe + NaOH Similarly, sodium selenide is readily oxidized to polyselenides, a conversion signaled by off-white samples. Sodium selenide reacts with acids to produce toxic hydrogen selenide gas. :Na2Se + 2 HCl → H2Se + 2 NaCl The compound reacts with electrophiles to produce the selenium compounds.
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Basic chromium sulfate is produced from chromate salts by reduction with sulfur dioxide, although other methods exist. The reduction could formally be written: :Na2Cr2O7 \+ 3 SO2 \+ H2O → Cr2(SO4)3 \+ 2 NaOH Since 33% of the anion charges are due to hydroxy ions the basicity is 33% (but in tanning jargon it is known as 33% reduced). Products with higher basicities, e.g. 42% or 50% may be obtained by the addition of sodium carbonate, these are often used in combination with sodium formate.
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The problem of "control" in the aldol addition is best demonstrated by an example. Consider the outcome of this hypothetical reaction: Hypothetical aldol reaction In this reaction, two unsymmetrical ketones are being condensed using sodium ethoxide. The basicity of sodium ethoxide is such that it cannot fully deprotonate either of the ketones, but can produce small amounts of the sodium enolate of both ketones. This means that, in addition to being potential aldol electrophiles, both ketones may also act as nucleophiles via their sodium enolate.
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In order to obtain a suitable reactivity, the obtained fragments are ground to reach the same fineness as Portland cement. The main components of blast furnace slag are CaO (30-50%), SiO2 (28-38%), Al2O3 (8-24%), and MgO (1-18%). In general increasing the CaO content of the slag results in raised slag basicity and an increase in compressive strength. The MgO and Al2O3 content show the same trend up to respectively 10-12% and 14%, beyond which no further improvement can be obtained.
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GLODAP climatology). Alkalinity (from Arabic "al-qalī") is the capacity of water to resist changes in pH that would make the water more acidic. (It should not be confused with basicity which is an absolute measurement on the pH scale.) Alkalinity is the strength of a buffer solution composed of weak acids and their conjugate bases. It is measured by titrating the solution with a monoprotic acid such as HCl until its pH changes abruptly, or it reaches a known endpoint where that happens.
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If this information does not allow unequivocal identification of the protein, its peptides can be subject to tandem mass spectrometry for de novo sequencing. Small changes in mass and charge can be detected with 2D-PAGE. The disadvantages with this technique are its small dynamic range compared to other methods, some proteins are still difficult to separate due to their acidity, basicity, hydrophobicity, and size (too large or too small). The second method, high performance liquid chromatography is used to fractionate peptides after enzymatic digestion.
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The Carlsberg Laboratory was known for isolating Saccharomyces carlsbergensis, the species of yeast responsible for lager fermentation, as well as introducing the concept of pH in acid-base chemistry. The Danish chemist Søren Peder Lauritz Sørensen introduced the concept of pH, a scale for measuring acidity and basicity of substances. While working at the Carlsberg Laboratory, he studied the effect of ion concentration on proteins, and understood the concentration of hydrogen ions was particularly important. To express the hydronium ion (H3O+) concentration in a solution, he devised a logarithmic scale known as the pH scale.
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The presence of two activating groups also make the benzene ring highly reactive toward electrophilic aromatic substitution. As the substituents are ortho, para-directing and para with respect to each other, all positions on the ring are more or less equally activated. The conjugation also greatly reduces the basicity of the oxygens and the nitrogen, while making the hydroxyl acidic through delocalisation of charge developed on the phenoxide anion. Paracetamol is part of the class of drugs known as "aniline analgesics"; it is the only such drug still in use today.
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Following elution, the protein readily binds DNA, indicating the protein's high affinity for DNA. Histone-like proteins were unknown to be present in bacteria until similarities between eukaryotic histones and the HU-protein were noted, particularly because of the abundancy, basicity, and small size of both of the proteins. Upon further investigation, it was discovered that the amino acid composition of HU resembles that of eukaryotic histones, thus prompting further research into the exact function of bacterial DNA binding proteins and discoveries of other related proteins in bacteria.
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Hybridisation theory is an integral part of organic chemistry, one of the most compelling examples being Baldwin's rules. For drawing reaction mechanisms sometimes a classical bonding picture is needed with two atoms sharing two electrons. Hybridisation theory explains bonding in alkenesOrganic Chemistry, Third Edition Marye Anne Fox James K. Whitesell 2003 and methane.Organic Chemistry 3rd Ed. 2001 Paula Yurkanis Bruice The amount of p character or s character, which is decided mainly by orbital hybridisation, can be used to reliably predict molecular properties such as acidity or basicity.
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As long as the nucleophilicity of the alkyl group does not lead to side reactions, catalytic amounts of Lewis acid are sufficient for many ene reactions with reactive enophiles. Nonetheless, the amount of Lewis acid can widely vary, as it largely depends on the relative basicity of the enophile and the ene adduct. In terms of solvent choice for the reactions, the highest rates are usually achieved using halocarbons as solvents; polar solvents such as ethers are not suitable, as they would complex to the Lewis acid, rendering the catalyst inactive.
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The catalyst accelerates the reaction by over one million fold, making it the most efficient supramolecular catalyst to date. It was proposed that such a high catalytic activity does not arise just from the increased basicity of the encapsulated substrate but also from the constrictive binding that stabilize the transition state of the cyclization. Unfortunately, this catalyst has a problem with product inhibition. To by pass that problem, the product of the cyclization reaction could be reacted with a dienophile transforming it into a Diels-Alder adduct that no longer fits inside the catalyst cavity.
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A dipole can align to stabilize or destabilize the formation or loss of a charge, thereby decreasing (if stabilized) or increasing (if destabilized) the activation barrier to a chemical event. Field effects can therefore tune the acidity or basicity of bonds within their fields by donating or withdrawing charge density. With respect to acidity, a common trend to note is that, inductively, an electron-withdrawing substituent in the vicinity of an acidic proton will lower the pKa (i.e. increase the acidity) and, correspondingly, an electron-donating substituent will raise the pKa.
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Reactions of the gas- phase dianions were studied by reacting with a small quantity of various reagents added to the helium carrier gas in the spectrometer. For example, reaction with deuterium oxide (heavy water) produced the singly-deuterated monanion C6H4(C22H)() identified as 126 m/z. Reaction with benzene produced the phenyl anion (77 m/z) highlighting the extreme basicity of the dianion. Attempted reaction with deuterium gas and deuterated methane was not successful despite the favourable thermodynamics; the authors attribute this to the high activation barrier for proton abstraction from those substrates.
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Distinguishing between both mechanisms requires consideration of inductive and mesomeric effects that could stabilize or destabilize a potential carbocation in the SN1 pathway. Usage of hydrohalic acids takes advantage of the fact that these agents are able to protonate the ether oxygen atom and also provide a halide anion as a suitable nucleophile. However, as ethers show similar basicity as alcohols (pKa of approximately 16), the equilibrium of protonation lies on the side of the unprotonated ether and cleavage is usually very slow at room temperature. Ethers can be cleaved by strongly basic agents, e.g.
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4-Dimethylaminopyridine (DMAP) is a derivative of pyridine with the chemical formula (CH3)2NC5H4N. This colourless solid is of interest because it is more basic than pyridine, owing to the resonance stabilisation from the NMe2 substituent. Because of its basicity, DMAP is a useful nucleophilic catalyst for a variety of reactions such as esterifications with anhydrides, the Baylis-Hillman reaction, hydrosilylations, tritylation, the Steglich rearrangement, Staudinger synthesis of β-lactams and many more. Chiral DMAP analogues are used in kinetic resolution experiments of mainly secondary alcohols and Evans auxiliary type amides.
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The first is basicity, which can be created by doing an alkali metal cation exchange. The second is the Si/Al ratio which impacts the cation exchange capacity. To get a higher adsorption capacity, there must be a lower Si/Al ratio in order to increase the cation exchange capacity. ZIFs 68, 69, 70, 78, 81, 82, 95, and 100 have been found to have very high uptake capacity, meaning that they can store a lot of carbon dioxide, though their affinity to it is not always strong.
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The reason for this large difference is that when one proton is removed from the cis isomer (maleic acid) a strong intramolecular hydrogen bond is formed with the nearby remaining carboxyl group. This favors the formation of the maleate H+, and it opposes the removal of the second proton from that species. In the trans isomer, the two carboxyl groups are always far apart, so hydrogen bonding is not observed. Section 6-2: Structural Effects on Acidity and Basicity Proton sponge, 1,8-bis(dimethylamino)naphthalene, has a pKa value of 12.1.
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For example, the expected (by electronic effects of methyl substituents) and observed in gas phase order of basicity of methylamines, Me3N > Me2NH > MeNH2 > NH3, is changed by water to Me2NH > MeNH2 > Me3N > NH3. Neutral methylamine molecules are hydrogen-bonded to water molecules mainly through one acceptor, N–HOH, interaction and only occasionally just one more donor bond, NH–OH2. Hence, methylamines are stabilized to about the same extent by hydration, regardless of the number of methyl groups. In stark contrast, corresponding methylammonium cations always utilize all the available protons for donor NH–OH2 bonding.
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Cells adjust their pHi accordingly upon an increase in acidity or basicity, usually with the help of CO2 or HCO3– sensors present in the membrane of the cell. These sensors can permit H+ to pass through the cell membrane accordingly, allowing for pHi to be interrelated with extracellular pH in this respect. Major intracellular buffer systems include those involving proteins or phosphates. Since the proteins have acidic and basic regions, they can serve as both proton donors or acceptors in order to maintain a relatively stable intracellular pH.
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Many eukaryotic proteins are post- translationally modified on their N-terminus. A common form of N-terminal modification is N-terminal methylation (Nt-methylation) by N-terminal methyltransferases (NTMTs). Proteins containing the consensus motif H2N-X-Pro- Lys- (where X can be Ala, Pro or Ser) after removal of the initiator methionine (iMet) can be subject to N-terminal α-amino-methylation. Monomethylation may have slight effects on α-amino nitrogen nucleophilicity and basicity, whereas trimethylation (or dimethylation in case of proline) will result in abolition of nucleophilicity and a permanent positive charge on the N-terminal amino group.
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It is prepared by the dehydrogenation of pyridine using Raney nickel: :2C5H5N → (C5H4N)2 \+ H2 Although uncoordinated bipyridine is often drawn with its nitrogen atoms in cis conformation, the lowest energy conformation both in solid state and in solution is in fact coplanar, with nitrogen atoms in trans position. Protonated bipyridine adopts a cis conformation. Upon complexation, the related N,N-heterocyclic ligand phenanthroline does not incur an enthalpic and entropic penalty, and thus its complexes tend to be more stable. With respective pKa's of 4.86 and 4.3 for their conjugate acids, phenanthroline and bipy are of comparable basicity.
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Nevertheless, the extreme acidity of this mixture is evident from the exceptionally poor proton-accepting ability of the species present in solution (hydrogen fluoride, normally not thought to have any appreciable Brønsted basicity at all, is in fact the strongest Brønsted base in the mixture). As a result, the acid is often said to contain "naked protons", though the "free" protons are, in fact, always bonded to hydrogen fluoride molecules. It is the fluoronium ion that accounts for fluoroantimonic acid's extreme acidity. The protons easily migrate through the solution, moving from H2F+ to HF, when present, by the Grotthuss mechanism.
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Due to the crucial role of base, specific amines must be added in excess or as solvent for the reaction to proceed. It has been discovered that secondary amines such as piperidine, morpholine, or diisopropylamine in particular can react efficiently and reversibly with trans-RPdX(PPh3)2 complexes by substituting one PPh3 ligand. The equilibrium constant of this reaction is dependent on R, X, a factor for basicity, and the amine's steric hindrance. The result is competition between the amine and the alkyne group for this ligand exchange, which is why the amine is generally added in excess to promote preferential substitution.
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Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) p 51 However, it has been shown that to define the order of Lewis base strength (or Lewis acid strength) at least two properties must be considered. Cramer, R. E., and Bopp, T. T. (1977) Great E and C plot. Graphical display of the enthalpies of adduct formation for Lewis acids and bases. Journal of Chemical Education 54 612-613 For Pearson's qualitative HSAB theory the two properties are hardness and strength while for Drago’s quantitative ECW model the two properties are electrostatic and covalent .
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Ball-and-stick model of the tetraamminediaquacopper(II) cation, [Cu(NH3)4(H2O)2]2+ Ammonia can act as a ligand in transition metal complexes. It is a pure σ-donor, in the middle of the spectrochemical series, and shows intermediate hard-soft behaviour (see also ECW model). Its relative donor strength toward a series of acids, versus other Lewis bases, can be illustrated by C-B plots.Laurence, C. and Gal, J-F. Lewis Basicity and Affinity Scales, Data and Measurement, (Wiley 2010) pp 50-51 IBSN 978-0-470-74957-9 The plots shown in this paper used older parameters.
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Compared to water, however, ammonia is more inclined to accept an H+ ion, and less inclined to donate one; it is a stronger nucleophile. Ammonia added to water functions as Arrhenius base: it increases the concentration of the anion hydroxide. Conversely, using a solvent system definition of acidity and basicity, water added to liquid ammonia functions as an acid, because it increases the concentration of the cation ammonium. The carbonyl group (C=O), which is much used in terrestrial biochemistry, would not be stable in ammonia solution, but the analogous imine group (C=NH) could be used instead.
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P4-t-Bu is an extremely hygroscopic solid which is thermally stable up to 120 °C and chemically stable to (dry) oxygen and bases. Traces of water and protic impurities can be eliminated by addition of bromoethane. The base is both very hydrophilic and very lipophilic and can be recovered easily and almost completely from reaction mixtures by the formation of the sparingly soluble tetrafluoroborate salt. Because of its extremely weak Lewis basicity, the cation of P4-t-Bu suppresses typical side reactions of metal organyls (such as aldol condensations) as can be caused by lithium amides such as lithium diisopropylamide (LDA).
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Dimethylaminoethyl acrylate is a acrylic acid ester carrying a functional group with basic properties. It therefore reacts as an α, β-unsaturated carbonyl compound in an addition reaction with nucleophiles in a Michael addition. As a reactive monomer, 2-dimethylaminoethyl acrylate forms homopolymers and copolymers with acrylic acid and acrylic acid salts, amides and esters, as well as methacrylates, acrylonitrile, maleic acid esters, vinyl acetate, chloroethene (vinyl chloride), 1,1-dichloroethene, styrene, 1,3-butadiene, unsaturated polyesters and drying oils. In copolymers, DMAEA improves their nucleophilicity, basicity, water solubility and adhesion to polar negatively charged substrates, as well as dyeability of acrylic fibers with anionic dyes.
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Compounds of cobalt in the +3 oxidation state exist, such as cobalt(III) fluoride , nitrate , and sulfate ; however, cobalt(III) chloride is not stable in normal conditions, and would decompose immediately into and chlorine.Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990. On the other hand, cobalt(III) chlorides can be obtained if the cobalt is bound also to other ligands of greater Lewis basicity than chloride, such as amines. For example, in the presence of ammonia, cobalt(II) chloride is readily oxidised by atmospheric oxygen to hexamminecobalt(III) chloride: :4 ·6 + 4 Cl + 20 + → 4 + 26 Similar reactions occur with other amines.
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The N-Si-N angle for the saturated tert-butyl substituted NHSi is 92°, slightly puckering C2 symmetric ring. The N-Si-N angle of the unsaturated analog is 90.5° (gas phase XRD) achieving a planar C2v ring. Upon saturation of the carbon backbone, the N-Si bonds shorten from 175.3pm to 171.9pm, shorter distances than would be expected for a single bond between nitrogen and divalent silicon. The longer bond in the unsaturated molecule is due to the nitrogens' lone pair electrons delocalization through the carbon π-bond, resulting in lower Lewis basicity of the nitrogen lone pairs toward the silicon, weakening and lengthening the N-Si bond.
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The matrix should not compete with the analyte molecule, so the matrix should not want to form the same type of ion as the analyte. For example, if the desired analyte has a high amount of acidity, it would be logical to choose a matrix with a high amount of basicity to avoid competition and facilitate the formation of an ion. The pH of the matrix can also be used to select what sample you want to obtain spectra for. For example, in the case of proteins, a very acidic pH can show very little of the peptide components, but can show very good signal for those components that are larger.
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Due to the basicity of the Se2− and Te2− ions, the alkali metal selenides and tellurides are alkaline in solution; when reacted directly with selenium and tellurium, alkali metal polyselenides and polytellurides are formed along with the selenides and tellurides with the and ions. They may be obtained directly from the elements in liquid ammonia or when air is not present, and are colourless, water-soluble compounds that air oxidises quickly back to selenium or tellurium. The alkali metal polonides are all ionic compounds containing the Po2− ion; they are very chemically stable and can be produced by direct reaction of the elements at around 300–400 °C.
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The advantages of this method include good separation of large molecules from the small molecules with a minimal volume of eluate, and that various solutions can be applied without interfering with the filtration process, all while preserving the biological activity of the particles to separate. The technique is generally combined with others that further separate molecules by other characteristics, such as acidity, basicity, charge, and affinity for certain compounds. With size exclusion chromatography, there are short and well-defined separation times and narrow bands, which lead to good sensitivity. There is also no sample loss because solutes do not interact with the stationary phase.
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Nitrogen is one of the most important elements in organic chemistry. Many organic functional groups involve a carbon–nitrogen bond, such as amides (RCONR2), amines (R3N), imines (RC(=NR)R), imides (RCO)2NR, azides (RN3), azo compounds (RN2R), cyanates and isocyanates (ROCN or RCNO), nitrates (RONO2), nitriles and isonitriles (RCN or RNC), nitrites (RONO), nitro compounds (RNO2), nitroso compounds (RNO), oximes (RCR=NOH), and pyridine derivatives. C–N bonds are strongly polarised towards nitrogen. In these compounds, nitrogen is usually trivalent (though it can be tetravalent in quaternary ammonium salts, R4N+), with a lone pair that can confer basicity on the compound by being coordinated to a proton.
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For other nucleophiles, most of the nucleophilic character came from their high polarizability, with little contribution from basicity, resulting in large α values. This observation led Pearson to develop his hard-soft acid- base theory, which is arguably the most important contribution that the Edwards equation has made to current understanding of organic and inorganic chemistry. Nucleophiles, or bases, that were polarizable, with large α values, were categorized as “soft”, and nucleophiles that were non-polarizable, with large β and small α values, were categorized as “hard”. The Edwards equation parameters have since been used to help categorize acids and bases as hard or soft, due to the approach’s simplicity.
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The converse is also possible as alleviation of alkalinity: electronegative atoms or species (such as fluorine or the nitro group) will have an "electron- withdrawal" effect and thereby reduce the basicity. To this end, trimethylamine is a more potent base than merely ammonia, due to the inductive effect of the methyl groups allowing the nitrogen atom to more readily accept a proton and become a cation being much greater than that of the hydrogen atoms. In guanidines, the protonated form (guanidinium) has three resonance structures, giving it increased stability and making guanidines stronger bases. Phosphazene bases also contain phosphorus and are, in general, more alkaline than standard amines and nitrogen-based heterocyclics.
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The reorganization of charge due to field effects will have the same result. An electric dipole field propagated through the space around, or in the middle of, a molecule in the direction of an acidic proton will decrease the acidity, while a dipole pointed away will increase the acidity and concomitantly elongate the X-H bond. These effects can therefore help to tune the acidity/basicity of a molecule to protonate/deprotonate a specific compound, or enhance hydrogen bond-donor ability for molecular recognition or anion sensing applications. Field effects have also been shown in substituted arenes to dominate the electrostatic potential maps, which are maps of electron density used to explain intermolecular interactions.
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Urea is a very poor chelating ligand due to low Lewis base character of its NH2 groups. However the carbonyl oxygens of Alaα170 and Alaα366 enhance the basicity of the NH2 groups and allow for binding to Ni2. Therefore, in this proposed mechanism, the positioning of urea in the active site is induced by the structural features of the active site residues which are positioned to act as hydrogen-bond donors in the vicinity of Ni1 and as acceptors in the vicinity of Ni2. The main structural difference between the Ciurli/Mangani mechanism and the other two is that it incorporates a nitrogen, oxygen bridging urea that is attacked by a bridging hydroxide.
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Sulfur dioxide is a versatile inert solvent widely used for dissolving highly oxidizing salts. It is also used occasionally as a source of the sulfonyl group in organic synthesis. Treatment of aryl diazonium salts with sulfur dioxide and cuprous chloride yields the corresponding aryl sulfonyl chloride, for example: :upright=2 As a result of its very low Lewis basicity, it is often used as a low-temperature solvent/diluent for superacids like Magic acid (FSO3H/SbF5), allowing for highly reactive species like tert-butyl cation to be observed spectroscopically at low temperature (though tertiary carbocations do react with SO2 above about –30 °C, and even less reactive solvents like SO2ClF must be used at these higher temperatures).
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Hexamethylbenzene has uses in various areas of chemical research. The oxidation of it to form 2,3,4,5,6,6-hexamethyl-2,4-cyclohexadienone (reportedly an intermediate in its formation from phenol) has been reported in Organic Syntheses using trifluoroperacetic acid or an acidic solution of hydrogen peroxide: center It has also been used as a solvent for 3He-NMR spectroscopy. Just as with benzene itself, the electron-rich aromatic system in hexamethylbenzene allows it to act as a ligand in organometallic chemistry. The electron-donating nature of the methyl groups—both that there are six of them individually and that there are six meta pairs among them—enhance the basicity of the central ring by six to seven orders of magnitude relative to benzene.
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Gallium is the lightest Group 13 metal with a filled d-shell, and has an electronic configuration of ([Ar] 3d10 4s2 4p1) below the valence electrons that could take part in d-π bonding with ligands. The somewhat high oxidation state of Ga in Ga(III)Br3, low electronegativity, and high polarizability allow GaBr3 to behave as a "soft acid" in terms of the Hard-Soft-Acid-Base (HSAB) theory. The Lewis acidity of all the gallium trihalides, GaBr3 included, has been extensively studied thermodynamically, and the basicity of GaBr3 has been established with a number of donors. GaBr3 is capable of accepting an additional Br− ion or unevenly splitting its dimer to form [GaBr4]−, a tetrahedral ion of which crystalline salts can be obtained.
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The former reaction may be carried out by either of the opposing glutamates, depending on the initial chirality of C1 in the hemithioacetal substrate; however, the second half is stereospecific and is carried out by only one of the opposing glutamates. It is worthy to note that the first theoretically confirmed mechanism for the R-substrate of glyoxalase one published recently. The catalytic mechanism of Glyoxalase have been studied by density functional theory, molecular dynamics simulations and hybrid QM/MM methods. The reason for the special specificity of the enzyme (it accepts both enantiomers of its chiral substrate but converts them to the same enantiomer of the product) is the higher basicity and flexibility of one of the active site glutamates (Glu172).
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They found that basic amino alcohols are ideally suited for this purpose, probably because amino groups effectively solvate phospholipids and basicity helps to preserve fluorescence signal. Amino alcohols have also beneficial effect when used for clearing of other tissues, which are mostly highly vascularized, and their opacity is given by absorption of light by hemoglobin on top of light scattering. Amino alcohols reduce pigmentation of those tissues very effectively by eluting the hem from hemoglobin. The original protocol is two- step incubation of fixed tissue in two different aqueous based clearing solutions, altogether taking one to two weeks. First solution, referred as ScaleCUBIC-1, CUBIC-1 or just reagent-1, is composed of N,N,N’,N’-tetrakis(2-hydroxypropyl)ethylenediamine (commercially under name Quadrol), urea and Triton X-100 in water.
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The TASF reagent or tris(dimethylamino)sulfonium difluorotrimethylsilicate is a reagent in organic chemistry with structural formula [((CH3)2N)3S]+[F2Si(CH3)3]−. It is an anhydrous source of fluoride and is used to cleave silyl ether protective groups. Many other fluoride reagents are known, but few are truly anhydrous, because of the extraordinary basicity of "naked" F−. In TASF, the fluoride is masked as an adduct with the weak Lewis acid trimethylsilylfluoride (FSi(CH3)3). The sulfonium cation ((CH3)2N)3S+ is unusually non-electrophilic due to the electron-donating properties of the three (CH3)2N substituents. This compound is prepared from sulfur tetrafluoride: :3 (CH3)2NSi(CH3)3 \+ SF4 -> 2 (CH3)3SiF + [((CH3)2N)3S]+[F2Si(CH3)3]− The colorless salt precipitates from the reaction solvent, diethyl ether.
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An example of alpha halogenation is the mono-bromination of acetone, carried out under either acidic or basic conditions, to give bromoacetone: Acidic (in acetic acid): 650px Basic (in aqueous NaOH): 650px In acidic solution, usually only one alpha hydrogen is replaced by a halogen, because each successive halogenation is slower than the first. The halogen decreases the basicity of the carbonyl oxygen, thus making protonation less favorable. However, in basic solution successive halogenations are more rapid due to inductive electron withdrawal by the halogen, making the remaining hydrogens more acidic. In the case of methyl ketones, this reaction often occurs a third time to form a ketone trihalide, which can undergo rapid substitution with water to form a carboxylate in what is known as the haloform reaction.
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Pseudothielavia terricola is a mesophilic fungus, with an optimal growth temperature of 37°C, a minimum growing temperature of 15°C and a highest of 46°C. Acidity and basicity also contribute greatly to the proper growth of the species, the fungi grows most well in a pH range between 3.9 - 6, and terminates growth in environment with a pH higher than 7.9 or lower than 2.9. As for nutrition, the species is capable of breaking down various types of carbohydrates - such as chitin, cellulose, and poly-/tri-/di-/monosaccharides -, alcohol, nitrate, ammonium, and nitrogen-containing compounds to support its growth. Mophologically, colonies grown on corn meal agar, malt extract agar, and oatmeal agar at 28°C display a well spread out uniform white mat in 14 days.
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N-glycosyltransferases are an unusual type of glycosyltransferase which joins single hexoses to the target protein. Attachment of sugars to the nitrogen atom in an amide group — such as the amide group of an asparagine — requires an enzyme, as the electrons of the nitrogen are delocalized in a pi-electron system with the carbon of the amide. Several mechanisms have been proposed for the activation. Among these are a deprotonation of the amide, an interaction between a hydroxyl group in the substrate sequon with the amide (a theory which is supported by the fact that the glycosylation rates appear to increase with the basicity of the second amino acid in the sequon) and two interactions involving acidic amino acids in the enzyme with each hydrogen atom of the amide group.
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C4 NADP-ME has been shown to be partially inhibited by its substrate, malate, suggesting two independent binding sites: one at the active site and one at an allosteric site. However, the inhibitory effect exhibits pH-dependence – existent at a pH of 7 but not a pH of 8. The control of enzyme activity due to pH changes align with the hypothesis that NADP-ME is most active while photosynthesis is in progress: Active light reactions leads to a rise in basicity within the chloroplast stroma, the location of NADP-ME, leading to a diminished inhibitory effect of malate on NADP-ME and thereby promoting a more active state. Conversely, slowed light reactions leads to a rise in acidity within the stroma, promoting the inhibition of NADP-ME by malate.
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With a formula weight of 86.8, BF is also conveniently the smallest weakly coordinating anion from the point of view of equivalent weight, often making it the anion of choice for preparing cationic reagents or catalysts for use in synthesis, in the absence of other substantial differences in chemical or physical factors. The anion is less nucleophilic and basic (and therefore more weakly coordinating) than nitrates, halides or even triflates. Thus, when using salts of , one can usually assume that the cation is the reactive agent and this tetrahedral anion is inert. owes its inertness to two factors: (i) it is symmetrical so that the negative charge is distributed equally over four atoms, and (ii) it is composed of highly electronegative fluorine atoms, which diminish the basicity of the anion.
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McGraw-Hill, NJ. Pharmacological experiments with TMA have been performed using one of its salts, typically the chloride, bromide or iodide, since these anions were not expected to interfere with the actions of the TMA cation. In the early pharmacological literature, however, there are references to the use of "tetramethylammonium hydroxide" or "tetramethylammonium hydrate", which were meant to facilitate comparison between weight-based dosages of different TMA salts, but did not involve the actual use of tetramethylammonium hydroxide, whose strong basicity would have been incompatible with physiological conditions. A thorough review of the pharmacology of TMA from a toxicological perspective, and current up to 1989, has been given by Anthoni and co-workers. Thus, the effects of TMA on nicotinic and muscarinic ACh receptors first stimulate, then block neurotransmission in sympathetic and parasympathetic ganglia, with depolarization.
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The pnictogens form trifluorides that increase in reactivity and basicity with higher molecular weight, although nitrogen trifluoride resists hydrolysis and is not basic.. The pentafluorides of phosphorus, arsenic, and antimony are more reactive than their respective trifluorides, with antimony pentafluoride the strongest neutral Lewis acid known.. Chalcogens have diverse fluorides: unstable difluorides have been reported for oxygen (the only known compound with oxygen in an oxidation state of +2), sulfur, and selenium; tetrafluorides and hexafluorides exist for sulfur, selenium, and tellurium. The latter are stabilized by more fluorine atoms and lighter central atoms, so sulfur hexafluoride is especially inert.. Chlorine, bromine, and iodine can each form mono-, tri-, and pentafluorides, but only iodine heptafluoride has been characterized among possible interhalogen heptafluorides. Many of them are powerful sources of fluorine atoms, and industrial applications using chlorine trifluoride require precautions similar to those using fluorine..
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Put simply, ion suppression describes the adverse effect on detector response due to reduced ionisation efficiency for analyte(s) of interest, resulting from the presence of species in the sample matrix which compete for ionisation, or inhibit efficient ionisation in other ways. Use of MS/MS as a means of detection may give the impression that there are no interfering species present, since no chromatographic impurities are detected. However, species which are not isobaric may still have an adverse effect on the sensitivity, accuracy and precision of the assay owing to suppression of the ionisation of the analyte of interest. Although the precise chemical and physical factors involved in ion suppression are not fully understood, it has been proposed that basicity, high concentration, mass and more intuitively, co-elution with the analyte of interest are factors which should not be ignored.
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According to the concept of glass developed by M. Shultz, in analogy with pH for aqueous solutions he proposed an innovative idea to establish for glasses and melts—the degree of acidity pO (negative logarithm of the activity of oxygen ions O2−) and standards for methods of measurement: pO is inversely proportional to the degree of basicity and concentration of the oxide. Under the guidance of M. Shultz developed are heat resistant inorganic coatings for the protection of structural materials of space technique (including military rockets, and for the spacecraft Buran) and lamellar coatings on semiconductor silicon for industrial electronics, organo- silicate corrosion-resistant, anti-icing, dielectric, thermal insulation, radiation proof covers for construction, electrical engineering and shipbuilding. Large enough the contribution of the scientist is in the sphere of developing new construction materials. M. Shultz is a founder one of Russian scientific schools.
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The complete structures for two of the four B toxins (B-II and B-IV) have been determined . Toxin B-II differs from B-IV in that the secondary structure of Toxin B-II contains about 15-20% less α-helixes than B-IV due to the differences in the primary structure of the two proteins; amino acids Ala in position 3, Ala in position 7 and Ala in position 8 in B-IV are substituted by amino acids Ser, Gly and Ser in B-II respectively. No homology is displayed with other sodium channel selective toxins, such as scorpion and sea anemone venom toxins, despite being similar in size, basicity, and degree of cross-linking. The secondary structures of scorpion and anemone toxins are largely organized into β-sheet conformations, while the secondary structures of B toxins organize in α-helical conformations Howell, M. L., Blumenthal, K. M. (1991).
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P4-t-Bu is one of the strongest neutral nitrogenous bases with an extrapolated pKa value of 42.1 in acetonitrile and is compared to the strong base DBU with a pKa value of 24.3 by 18 orders of magnitude more basic. The compound is very well soluble in non-polar solvents, such as hexane, toluene or tetrahydrofuran, and is usually commercially available as a 0.8 to 1 molar solution in hexane. Already in weakly acidic media protonation produces the extremely delocalized and soft P4-t-Bu-H cation and causes besides a very strong solubilization effect also an extreme acceleration of addition reactions even at temperatures below -78 °C. P4-t-Bu owes its extraordinarily high basicity with low nucleophilicity to its very high steric hindrance and the involvement of many donor groups in conjugation with the spatially demanding structure of the cation formed by protonation.
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Although rechargeable, the produced at the cathode is generally insoluble in the organic electrolyte, leading to buildup along the cathode/electrolyte interface. This makes cathodes in aprotic batteries prone to clogging and volume expansion that progressively reduces conductivity and degrades battery performance. Another issue is that organic electrolytes are flammable and can ignite if the cell is damaged. Although most studies agree that is the final discharge product of non-aqueous Li-O2 batteries, considerable evidence that its formation does not proceed as a direct 2-electron electroreduction to peroxide O (which is the common pathway for O2 reduction in water on carbon) but rather via a one–electron reduction to superoxide O, followed by its disproportionation: Superoxide (O) has traditionally been considered as a dangerous intermediate in aprotic oxygen batteries due to its high nucleophilicity, basicity and redox potential However, reports suggest that LiO2 is both an intermediate during the discharge to peroxide () and can be used as the final discharge product, potentially with an improved cycle life albeit with a lower specific energy (a little heavier battery weight).
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If its OH group is eliminated or its position is changed the binding affinity is reduced. The triphenylethylene moiety and the side chain are required for tamoxifen binding to the ER, whereas for 4-hydroxytamoxifen, the side chain, and the phenyl-propene do not appear as crucial structural elements for binding to the ER. The basicity and length of the side chain do not seem to play a crucial role for tamoxifen binding affinity to the ER nor the β-ring of tamoxifen, but the stilbene moiety of tamoxifen is necessary for binding to the ER. The hydroxyl group is of particular importance for ER binding of 4-hydroxytamoxifen, and the ethyl side chain of tamoxifen protrudes out of the ligand-binding domain of the ER. Few tamoxifen users have suffered from increased rates of uterine cancer, hot flushes, and thromboembolisms. The drug can also cause hepatocarcinomas in rats. This is likely due to the ethyl group of the tamoxifen stilbene core that is subject to allylic oxidative activation causing DNA alkylation and strand scission.
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