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JEE Advanced levelSingle correct optionDifficulty 3 of 3hc216

To prepare n-butylbenzene from benzene without rearrangement, the best method is:

A1-Chlorobutane with anhydrous $AlCl X_{3}$
BButanoyl chloride with $AlCl X_{3}$ , then $Zn (Hg) / conc \cdot HCl$
CBut-1-ene with $H X_{3} PO X_{4}$
DButanoyl chloride with $AlCl X_{3}$ , then $NaBH X_{4}$

Answer: B

Direct alkylation via a primary carbocation or alkene protonation rearranges to the sec-butyl cation. Acylation gives the unrearranged ketone

C X_{6} H X_{5} - CO - CH X_{2} CH X_{2} CH X_{3}

, and Clemmensen reduction converts

C = O

to

CH X_{2}

.

NaBH X_{4}

would give only the alcohol.

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