Inductive effect, on acid

The influence of the inductive effect on acidity is best understood in terms of the conjugate base, RCOO, and can be summarized as follows ... 

Electron-withdrawing groups increase acid strength electron-donating groups decrease acid strength, C. Inductive Effects on Acidity... 

ACIDITY OF CARBOXYLIC ACIDS Resonance Stabilization of the Carboxylate Ion Inductive Effect on Acidity Acidity of Aromatic Carboxylic Acids... 

Proton acid-base reactions are not particularly sensitive to stoic compression, and hence provide a good measure of inductive effects. For acid-base character, three sets of reference reactions can be used. The easiest of these to perform experimentally requires an analogy be drawn between the relative pK values of a series of protonated annelated pyridines and the pK values of the analogous isoelectronic benzene. The second is a direct measure of the kinetic acidity of the a- and P-sites on a soies of annelated benzenes. The third is a related direct assessment of kinetic acidity by protodetritiation. 

Fluoroalkylamines react with nitrous acid to produce the corresponding unstable fluoroahphatic diazomum ions Placement of the tnfluoromethyl group at a carbon position a, (i, or y to a diazomum ion was used to probe the inductive effect on the chemistry of the transient carbocation resulting from dediazomation [7] If the fluoroalkyl group is bound to the same carbon as the amino group, conversion to the more stable diazo compound occurs For example, 4-diazo-l,l,l,2,2-pentafluoro-3-pentafluoroethyl-3-tnfluoromethylbutane is obtained from the reaction of the poly-fluoroalkylamine salt with sodium nitrite [8, 9] (equation 8)... 

Fig. Inductive effect on the conjugate base of trichloroacetic acid.

Table 4.1 Inductive Effects on the Acid Strength of Some Carboxylic Acids...

The magnitude of a substituent effect depends on its distance from the carboxyl group. Substituents on the a carbon atom are most effective in increasing acid strength. More distant substituents have smaller effects on acidity, showing that inductive effects decrease rapidly with distance. 

Early gas phase data represented an important contribution to the understanding of solvent effects on acidity/basicity. In aqueous solution the basicity order was known to be (CH3)3N <(CH3)2NH >CH3NH2, and it was recognised that this is not the anticipated inductive order. The advent of Munson s gas phase order, (CH3)3N >(CH3)2NH >CH3NH2, settled the case by pointing out that only differences in solvation energies could explain the irregular solution behaviour [24]. 

The 11 /3-OH of hydrocortisone is of major importance in binding to the receptors. Cortisone is reduced in vivo to yield hydrocortisone as the active agent. The increased activity of 9o. halu derivatives may be due to the electron-withdrawing inductive effect on the I IjS-OH. making it more acidic and. therefore, better able to form hydrogen bonds with the recep-... 

Studying substituent effects on acidity is the standard method of determining whether a group is donating or withdrawing by induction and resonance,... 

The effects of meso substituents on the acidities of benzimidazoles have been examined by potentiometric titration of a series of 2-substituted benzimidazoles in acetonitrile. The 2-substituents appear to exert primarily inductive effects on the acidity centre, with the pAg dependent on glass electrodes are inaccurate at pH values of > 11 in water (these compounds are very weak acids). As acetonitrile has a self-protolysis constant, pAg, of 33.3 (cf. water, pAg 14) it becomes possible to study the acidic properties of such slightly dissociated compounds. In... 

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