Question

How will you obtain Benzoic Acid from the following?
 (i) Toluene 
(ii) Benzamide 
(iii) Ethyl benzoate 
 

Hint:

Oxidation of side chains (toluene) and hydrolysis of amides/esters are standard methods to prepare benzoic acid.

Answer 1

(i) From Toluene:
Toluene is oxidized with alkaline or acidic KMnO$_4$ to form benzoic acid.
\[ C_6H_5CH_3 \; \xrightarrow{[O], KMnO_4} \; C_6H_5COOH \] (ii) From Benzamide:
Benzamide undergoes hydrolysis in the presence of dilute acid or alkali to give benzoic acid.
\[ C_6H_5CONH_2 + H_2O \; \xrightarrow{H^+ / OH^-} \; C_6H_5COOH + NH_3 \] (iii) From Ethyl Benzoate:
Ethyl benzoate undergoes acidic or basic hydrolysis to give benzoic acid.
\[ C_6H_5COOC_2H_5 + H_2O \; \xrightarrow{H^+ / OH^-} \; C_6H_5COOH + C_2H_5OH \] Conclusion:
Benzoic acid can be prepared by oxidation of toluene, hydrolysis of benzamide, and hydrolysis of ethyl benzoate.