The following reaction of benzene with carbon monoxide and hydrogen chloride in the presence of aluminum trichloride to give benzaldehyde is known as

Gatterman-Koch reaction

The correct answer is Option (2) → Gatterman-Koch reaction

The reaction shown is:

Benzene + CO + HCl in the presence of anhydrous AlCl₃ and CuCl → Benzaldehyde (–CHO group introduced).

This reaction is called the Gattermann–Koch reaction.

Benzene reacts with carbon monoxide and hydrogen chloride in the presence of AlCl₃ and CuCl to introduce a formyl group (–CHO) forming benzaldehyde.

OTHER OPTIONS

• Kolbe reaction – used for carboxylation of phenoxide ions to form salicylic acid.

• Williamson ether synthesis – used for preparing ethers from alkoxides and alkyl halides.

• Friedel–Crafts reaction – introduces alkyl or acyl groups, not specifically the –CHO group using CO and HCl.