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In the following reaction sequence starting from 4-methylaniline (CH3-C6H4-NH2, para isomer): Step 1: NaNO2 + HCl at 0-5 deg C -> [A] Step 2: [A] + Cu2Cl2 + HCl -> [B] Step 3: [B] + Cl2/hv -> [C] (major product) Identify compound [C].

1. 4-chloro benzyl chloride (ClCH2-C6H4-Cl, para)
2. 4,4'-dimethyl biphenyl (CH3-C6H4-C6H4-CH3)
3. 4-chloro-1-(chloromethyl)benzene
4. 1-chloro-4-(dichloromethyl)benzene

Correct answer: 4-chloro benzyl chloride (ClCH2-C6H4-Cl, para)

Solution

4-methylaniline (para-toluidine) is diazotized with NaNO2/HCl at 0-5 deg C to give 4-methylbenzenediazonium chloride [A]. Sandmeyer reaction: [A] + Cu2Cl2/HCl replaces -N2+Cl- with -Cl to give 4-chlorotoluene [B] (Cl on ring, CH3 on ring, para). Chlorination of [B] with Cl2/hv proceeds by free-radical mechanism, preferentially at the benzylic CH3 position (lower bond dissociation energy). Major product [C] = ClCH2-C6H4-Cl (para) = 4-chlorobenzyl chloride.

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