2. Conversion into functional derivatives
(a) Conversion into acid chlorides
Benzoyl chloride is prepared from benzoic acid by
(A) Cl2, (B) SO2Cl2
(C) SOCl2 (D) Cl2, H2O
(b) Conversion into esters
Conversion into Esters (Esterification):
Carboxylic acid on reacting with alcohols in presence of dehydrating agent (H2SO4 or dry HCl gas) gives esters. The reaction is known as esterification.
This reaction is reversible and the same catalyst, hydrogen ion, that catalyzes the forward reaction, esterification, necessarily catalyzes the reverse reaction hydrolysis.
The equilibrium is particularly unfavourable when phenols (ArOH) are used instead of alcohol; yet if water is removed during the reaction, phenolic esters [RCOOAr] are obtained in high yield.
The presence of bulky group near the site of reaction, whether in alcohol or in the acid, slows down esterification (as well as its reverse, hydrolysis).
Reactivity CH3OH > 1° > 2° > 3°
In esterification HCOOH > CH3COOH > RCH2COOH > R2CHCOOH > R3CCOOH