See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Concept: When a molecule contains both an amine (N-H) and an alcohol (O-H) group and is treated with an acyl chloride (acid chloride), chemoselectivity determines which nucleophile reacts preferentially. Amines are generally much stronger nucleophiles than alcohols. However, the reagent shown is chloroacetyl chloride (ClCH2COCl). The question asks for the major product. Step 1 - Identify the nucleophilic sites: The substrate is a 3-substituted piperidine bearing both a secondary amine (N-H in the ring) and a primary alcohol (CH2-OH at C-3). Both can react with the acid chloride. Step 2 - Reactivity comparison: Secondary amines are far more nucleophilic than primary alcohols under normal conditions. Therefore, the nitrogen of the piperidine ring reacts preferentially with the chloroacetyl chloride (ClCH2C(=O)Cl). Step 3 - Product of N-acylation: The nitrogen attacks the carbonyl carbon of ClCH2COCl, displacing Cl- and forming an N-acyl (amide) product. The CH2-OH group at C-3 remains unreacted. This gives the product where N bears the -C(=O)-CH3 group (acetyl from chloroacetyl chloride, but here the reagent is written as CH2-C(=O)-Cl, i.e., chloroacetyl chloride giving -C(=O)-CH3 after HCl loss — actually the acyl group from CH3COCl is acetyl, -C(=O)CH3). The nitrogen is acylated, and the hydroxymethyl group remains free. Step 4 - Match to options: Option (b) shows the piperidine nitrogen bearing a -C(=O)-CH3 group (N-acetylated) with the CH2-OH group intact at C-3. This matches N-acylation as the major product. Why other options fail: - Option (a): O-acylation of the alcohol while N-H remains free — this would be the minor product since nitrogen is more nucleophilic than oxygen. - Option (c): An elimination product (exocyclic alkene) — there is no reason for elimination under these mild acylation conditions. - Option (d): A ketone at C-3 — this would require rearrangement or oxidation, not simple acylation. Therefore, the correct answer is B.