Induction effect, acetone

Peroxybenzoic acid readily oxidizes aryl and alkyl sulphoxides in acetone, methylene chloride or chloroform solutions, to the sulphone in high yield . The reaction is second order and acid catalysed as is the reaction with peracetic acid . The rate of oxidation is about five times faster than when peracetic acid is used. Other work considering the oxidation of sulphoxides with peracids gathered kinetic evidence and showed that the reaction was indeed second order and that the reaction involved nucleophilic attack by the sulphoxide sulphur atom on the peracid moiety. A further study by the same authors showed that with benzyl and phenyl alkyl sulphoxides the rate of reaction was very sensitive to the inductive effect of the alkyl group. Support for the nucleophilic attack by the sulphur atom on the peracid in acidic solution was forthcoming from other sources . ... 

Acetone is a very weak acid (fCa approximately 10-19), but the presence of an oxygen atom bound to the adjacent carbon atom produces an inductive effect that makes it considerably more acidic than is a... 

However, solvation and entropy (which could be very different between these two types of amines) must be taken into account when comparing the two methods (titration and infrared spectroscopy). The ionization constants of a series of silylmethylpiperidines and their carbon analogs were measured potentiometric ally in methanol. The data indicates a lower basicity for these compounds, compared to non-silylated analogs, which was explained in terms of inductive effects, three-center-bond formation and (p-d)cr interactions.26 From a study of the effect of solvation by acetone on the basicity of... 

Oximes behave analogously to carbonyls in their reactions with e q, and their log k versus inductive effect of the OH group on the nitrogen atom. This effect lowers the dipole moment from 1-3 Debye units (D) for propylamine to 0-9 for acetoxime. By contrast, the dipole moments increase from 1-6 D for propan-2-ol to 2-9 for acetone. 

An important example of this effect is the decrease in equilibrium constants for ketones as compared to aldehydes. The replacement of the aldehyde hydrogen of acetaldehyde (K = 1.3) with a methyl group, to produce acetone (K = 2 X 10-3), results in a decrease in the equilibrium constant for hydration by a factor of approximately 1000. The inductive effect of the electron-donating alkyl group also helps shift the equilibrium for ketones toward the reactant. 

Comparison of the overall rate constants (when ionisation occurs along two competitive paths) or of the rate constants (when there is only one enolisation site) with that of a parent unsubstituted methyl ketone, e.g. acetone or acetophenone, shows that an alkyl group usually decreases ketone reactivity under conditions of base catalysis. This is in agreement with a small electron-repelling inductive effect which makes the carbanion ion less stable (e.g. the halogenation rate constant decreases by a factor of 6.5 on going from acetophenone to propiophenone when the reaction is catalysed by acetate ion [acetic acid-water 75 25 at 25°CI (Evans and Gordon, 1938). However, the factor is very small and could be explained by steric effects as well. 

A great number of data on inductive effects in the aliphatic series have been reported. Broadly speaking, results are in agreement with what is expected from the anionic and cationic characters of the transition states an electron-withdrawing substituent increases the rate of the base-promoted ionisation, whereas it retards that of acid-catalysed enolisation. For instance, a bromine atom at the exposition modifies the rate constants of acetate and HCl-catalysed bromination of acetone in water by factors of 4400 and 1/6.5, respectively (R. A. Cox and Warkentin, 1972 Watson and Yates, 1932). 

Nevertheless, the inductive effect of a substituent is independent of the solvent used. Therefore, the slope of the linear correlations for water, acetone, and acetonitrile is the same (Figs. 49 and 50). The E values increase in the organic solvents (acetone and AN). This fact may be attributed to a greater stabilization of the oxidation +2 state of the clathrochelates in these solvents. 

A comparison of the ff, values (Table XII) obtained by using CCI4 and acetone or DMSO as solvents illustrates the strong influence of the medium on the value of the inductive effect of substituted pyrimidinyl groups. The best agreement between the (t, values has been noted for solvents of the same type, such as acetone and DMSO (82MI1). 

Aldol addition reactions of ketones are rarely successful, since they are usually endoergonic. For example, the base-mediated aldolization of acetone provides only a few percent of the aldol, diacetone alcohol (equation 26). However, the conversion may be accomplished in 75% yield by refluxing acetone under a Soxhlet extractor containing calcium or barium hydroxide. - On the other hand, di-methoxyacetone dimerizes under basic conditions to the aldol, with an equilibrium constant significantly greater than unity (K = 10 dm mol equation 27). The difference in equilibrium constants of equations (26) and (27) parallels the equilibrium constants for hydration of the two ketones, and results from the inductive effect of the methoxy groups. 

The values of K, thus derived can in many cases be interpreted in terms of molecular structure. The increase in acidity ( 4 pK units) produced by introducing a halogen atom into acetone can be classified as an inductive effect, depending upon the stabilization of the anion by interaction between its charge and the carbon-halogen dipole, e.g.,... 

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