Question

Which of the following represents the Gattermann-Koch reaction?

• A. \( \text{Introduction of a formyl group (-CHO) to an aromatic compound using CO and HCl in the presence of AlCl}_3 \text{ or CuCl.} \)
• B. \( \text{Reduction of a nitro group to an amine group.} \)
• C. \( \text{Introduction of an acyl group (-COCH}_3) \text{ to an aromatic ring.} \)
• D. \( \text{Halogenation of an aromatic compound in the presence of a Lewis acid.} \)

Hint:

The Gattermann-Koch reaction is a useful method for introducing a formyl group to aromatic compounds. The reaction requires CO, HCl, and a Lewis acid catalyst such as \( \text{AlCl}_3 \) or \( \text{CuCl} \).