See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Tertiary amines react with nitrous acid (generated from NaNO2 + HCl) differently from primary and secondary amines. Secondary amines form stable N-nitrosamines (R2N-N=O). Primary amines form diazonium salts. Tertiary amines, however, cannot form a stable nitrosamine because there is no N-H bond to replace. Instead, tertiary amines react with nitrous acid (NO+) to form N-nitroso ammonium salts — the nitrosonium ion (NO+) attacks the nitrogen lone pair of the tertiary amine, forming a quaternary-like N-nitroso ammonium species. Step 1: Identify the starting material. The starting material is tribenzylamine: N(CH2Ph)3, a tertiary amine with three benzyl substituents on nitrogen and no N-H bond. Step 2: Reaction conditions. NaNO2 + HCl generates nitrous acid (HNO2), which further generates the nitrosonium ion (NO+) in acidic solution. Step 3: Reactivity of tertiary amines with NO+. Since there is no N-H in a tertiary amine, the classical nitrosamine formation (which requires replacement of N-H) cannot occur. Instead, NO+ acts as an electrophile and attacks the lone pair on nitrogen of the tertiary amine, forming an N-nitroso ammonium salt: [R3N-N=O]+. This is the characteristic reaction of tertiary amines with nitrous acid — they form N-nitrosoammonium salts rather than neutral nitrosamines. Step 4: Product identification. The product is Ph-CH2-N(+)(CH2-Ph)(CH2-Ph)(N=O), which is the N-nitrosoammonium salt of tribenzylamine. This corresponds to option (c). Step 5: Why other options fail. - Option (a): This is a neutral N-nitrosamine with only two benzyl groups, implying loss of one benzyl group — this does not occur under these conditions. - Option (b): This is N-benzyl-N-phenyl-N-nitrosamine, which would require a phenyl group on nitrogen — not present in tribenzylamine. - Option (d): Nitrosobenzene would require complete degradation and is not the product of this reaction. At 90°C with HCl, the N-nitrosoammonium salt (option c) is the product formed from the tertiary amine tribenzylamine reacting with the nitrosonium ion. Therefore, the correct answer is C.