See image — Amines Chemistry Question

💡 Solution & Explanation

Concept: Phase Transfer Catalysis (PTC) The reaction involves converting a primary alkyl bromide (1-bromodecane, CH3(CH2)8CH2Br) to a nitrile (CH3(CH2)8CH2CN) using KCN in benzene. The challenge here is that KCN is an ionic salt (water-soluble, polar) while the alkyl bromide and benzene are nonpolar/organic. This creates a two-phase problem: the nucleophile (CN-) resides in the aqueous/ionic phase and cannot easily react with the substrate in the organic phase. Step 1 - Identify the type of catalyst needed: For such reactions, a phase transfer catalyst (PTC) is required. A PTC shuttles anions (like CN-) from the ionic phase into the organic phase, enabling the SN2 reaction to proceed efficiently. Step 2 - Features of an effective PTC: A phase transfer catalyst is typically a quaternary ammonium salt. It has a positively charged nitrogen center that can associate with the CN- anion and a lipophilic (organic-soluble) organic framework that allows it to carry the ion pair into the organic (benzene) phase. Step 3 - Evaluate each option: (a) Benzyl chloride (PhCH2Cl) - This is an alkyl halide, not a quaternary ammonium salt. It cannot act as a PTC. It might alkylate CN- but is not a catalyst. (b) Aniline (PhNH2) - This is a primary amine, not a quaternary ammonium salt. It lacks the permanent positive charge needed to shuttle anions. Not a PTC. (c) Benzyltrimethylammonium chloride (PhCH2N+(CH3)3 Cl-) - This IS a quaternary ammonium salt with a permanent positive charge. The lipophilic benzyl and methyl groups allow it to partition into the organic phase, carrying CN- along with it, enabling the SN2 reaction in benzene. This is a classic phase transfer catalyst. (d) Acetanilide (PhNHCOCH3) - This is an amide, not a quaternary ammonium salt. It has no permanent positive charge and cannot function as a PTC. Step 4 - Conclusion: Option (c), benzyltrimethylammonium chloride, is a quaternary ammonium salt and functions as a phase transfer catalyst by transferring CN- from the ionic environment into the organic benzene phase, dramatically accelerating the SN2 reaction. Therefore, the correct answer is C.