Question

$n$-Propyl benzene can be obtained in quantitative yield by following method:
(i) By treating benzene with n-propyl chloride in presence of $AlCl_3$
(ii) By treating excess of benzene with n-propyl chloride in presence of $AlCl_3$
(iii) By treating benzene with allyl chloride in presence of $AlCl_3$ followed by reduction
(iv) By treating benzene with propionyl chloride in the presence of $AlCl_3$ followed by Clemmensen reduction.

• A. By $(ii), (iii)$ and $(iv)$
• B. By $(i), (iii)$ and $(iv)$
• C. By $(iii)$ and $(iv)$
• D. By $(ii)$ only

Answer 1

Answer: (C)

$(i)$ and $(ii)$ methods will form isopropyl benzene because $n$-propyl carbocation, being less stable, rearranges to the more stable $(2°)$ isopropyl carbocation. Moreover, method $(i)$ will lead to polyalkylation. Methods $(iii)$ and $(iv)$ can be used for preparing $n$-propyl benzene.