Question

Identify the reagent(s) for the conversion of chlorobenzene to 3-chlorobenzaldehyde.

(a) CrO3 and (CH3CO)2O

(b) CrO2Cl2; H2O

(c) Cl2/hv; H2O

(d) CO, HCl and CuCl

The question was posed to me by my college director while I was bunking the class.

This interesting question is from Preparation of Aldehydes and Ketones topic in section Aldehydes, Ketones and Carboxylic Acids of Chemistry – Class 12

Answer 1

Right choice is (d) CO, HCl and CuCl

The best I can explain: When benzene or its derivative is treated with CO and HCl in the presence of anhydrous AlCl3 or CuCl, it gives a benzaldehyde or substituted benzaldehyde. This is known as Gatterman-Koch reaction.