The Gatterman reaction is a formylation reaction in which a diazonium salt reacts with carbon monoxide (CO) and hydrogen chloride (HCl) in the presence of a Lewis acid (usually AlCl₃). This reaction results in the formation of an aryl aldehyde. However, when a halide is used instead of the formylating agent, the reaction can produce a haloarene.
For the given options:
- Haloarene: A diazonium salt reacts with a halogen (like Cl, Br, or I) to form a haloarene (a compound where a halogen is attached to an aromatic ring).
- Aryl amine: The product of a diazonium reaction would typically not give an aryl amine, as it is formed from a primary amine before it is diazotized.
- Phenol: Phenol would be formed in a reduction reaction (like the Sandmeyer reaction) but not as a major product in the Gatterman reaction.
- Diphenyl ether: This is not a major product of the Gatterman reaction.
Thus, the major product formed when diazonium salt undergoes the Gatterman reaction is haloarene.