Question

Write the preparation of benzoic acid from the following: 
a. styrene
b. benzamide
c. dry ice

Answer 1

a. Preparation of benzoic acid from styrene:
Acidic potassium dichromate or acidic potassium permanganate oxidizes styrene (phenylethene) into benzoic acid.

b. Preparation of benzoic acid from benzamide:
Benzamide on hydrolysis in dilute acidic or alkaline medium gives benzoic acid.

c. Preparation of benzoic acid from dry ice:
When the solution of phenyl magnesium iodide in dry ether is added to dry ice ( solid CO₂ ), it gives a complex (magnesium salt of carboxylic acid), which on acid hydrolysis gives benzoic acid.