Methyl chloride on treatment with excess of ammonia yields

Methylamine

The correct answer is Option (1) → Methylamine

Alkyl halides react with ammonia via nucleophilic substitution reaction.

Methyl chloride reacts with ammonia to form methylamine. CH₃Cl + NH₃ → CH₃NH₂

However, methylamine formed is more nucleophilic than ammonia and can further react with methyl chloride to form secondary and tertiary amines.

But when excess ammonia is used: Ammonia suppresses further alkylation by competing with methylamine for reaction with methyl chloride. Thus, the reaction stops mainly at primary amine stage. Hence, methylamine is the major product.

Option 1: Methylamine -- Formed as primary product. Excess ammonia prevents further substitution. Correct.

Option 2: Dimethylamine -- Forms only if further alkylation occurs. Suppressed in excess ammonia. Incorrect.

Option 3: Trimethylamine-- Requires multiple alkylation steps. Not favored in excess ammonia. Incorrect

Option 4: Mixture of methylamine, dimethylamine and trimethylamine--  Occurs when ammonia is not in excess. Incorrect.