Question

The following reagent is used for introducing a formyl group $(?CHO)$ into the benzene ring

• A. $CO + HCl$
• B. $HCN + HCl$
• C. Both $(a)$ and $(b)$
• D. None of the above

Answer 1

Answer: (C)

Both $(a)$ and $(b)$

Answer 2

Gattermann-Koch formyladon When a mixture of $CO$ and $HCl$ gas is passed through a solution of benzene in the presence of anhydrous $AlCl_3$ and $CuCl$, benzaldehyde is formed.
$CO + HCl {->} \underset{\text{formyl chloride}}{[HCOCl]}$

If $CO$ in this reaction is replaced by $HCN$, the reaction is called Gattermann formylation.