(c) : Effect of substituent on the acid strength of aliphatic acids:
(i) Acidity decreases as the +I - effect of the alkyl group increases.
HCOOH > CH3COOH > (CH3)2CHCOOH > (CH3)3 CCOOH
(ii) Acidity decreases as the –Ieffect as well as number of halogen atoms decreases.
FCH2COOH > ClCH2COOH > BrCH2COOH > ICH2COOH > CH3COOH
F3CCOOH > F2CHCOOH > FCH2COOH > CH3COOH
(iii) Electron donating substituents like – R, – OH, – NH2 etc. tend to decrease while electron withdrawing substituents like –NO2, –CHO etc. tend to increase the acid strength of substituted acid. On the basis of given information the relative order of increasing acid strength of the given compounds is
(CH3)2COOH < CH3COOH < CH3OCH2COOH < CF3COOH
