(a) Give the order of rectivity towards `S_(N^(1))` solvolysis of the following :
(i) Benzyl chloride (ii) p- chlorobenzyl chloride
(iii) p- Methoxybezyl chloride (iv) p- Methylbenzyl
Chloride (v) p- Nitrobenzyl chloride.
(b) Explain :

Explanation

(a) solvolysis means the replacement of CI by solvent anion . In `S_(N^(1))` mechanis, a carbocation is formed as the intermediate. The stability of carbocation decides the reactivity . It is in the order : `III gt IV gt I gt II gt V`
An EDG increase the stability and hence reactivity while EWG decreases the stability (and hence reactivity) but in Structure IV, the stability of benzyl carbocation is due to hyperconjugation `+R " and " -I` effects of (-OMe) group are stronger than +I and hyperconjugation effects of the (-Me) group.

`3^(@)` Halide undergoes `S_(N^(1))` reactions and one of the product is `(HB hArr H^(+) +Br^(-))`. HBr releases `H^(+)` in solution and hence it is acidic in nature .

Aryl halides do not easily undergo nucleophilic substitution reaction So the solution remains neutal as `C_(2)H_(5)OH` is neutral.