The `S_(N^(1))` reactivity of the following halides will be in the order:
(i) `(CH_(3))_(3)C-Br`
(ii) `(C_(6)H_(5))CHBr`
(iii) `(C_(6)H_(5))_(2)C(CH_(3))Br`
(iv) `(CH_(3))_(2)CHBr`
(v) `C_(2)H_(5)Br`

Options

A. (v) gt (iv) gt (i) gt (ii) gt (iii)
B. (ii) gt (iii) gt (v) gt (i) gt (iv)
C. (i) gt (iii) gt (v) gt (ii) gt (iv)
D. (iii) gt (ii) gt (i) gt (iv) gt (v)

Answer

D

Explanation

More stable the carbocation more reactive is the alkyl halide in `S_(N^(1))` reaction. Since the stability of the carbocations decreases the order of their reactivity is
`(C_(6)H_(5))_(2)overset(+)(C )CH_(3)gt (C_(6)H_(5))_(2)CH^(+)gt(CH_(3))_(3)C^(+)gt(CH_(3))_(2)C_(2)^(+)H_(5)`, hence the reactivity of the alkyl halides decreases in the same order. So (iii) gt (ii) gt (i) gt (iv) gt (v) i.e., (C ) is correct.