Which of the following compounds will undergo racemisation when solution of KOH hydrolyses

Options

A. (iii) and (iv)
B. (i) and (iv)
C. Only (iv)
D. (ii) and (iv)

Answer

C

Explanation

In nucleophilic substitution reaction , racemisation generally occurs in `S_(N^1)` reaction , where as in case of `S_(N^2)` reaction , inversion of the configuration occurs.
(i) Benzyl chloride undergoes `S_(N^1)` reaction due to formation of stable benzyl carbocation . However , benzyl group does not show racemisation because of the absence of a chiral centre.
(ii) 1- chloropropane is a primary alkyl halide and undergoes `S_(N^2)` reaction . Hence it will not show any racemisation .
(iii) 1-chloro-2-methyl propane is also a primary alkyl halide .
(iv) 2-chlorobutane is a secondary alkyl halide and possesses one chiral centre . Therefore it will undergo racemisation reaction by `S_(N^1)` mechanism :