Mustard gas `(ClCH_2CH_2)_2-S` hydrolysed by water to `Cl(CH_2)_2 S(CH_2)_2 OH` much faster than expected for a primary halide. Offer an explanation.

Explanation

Neighbouring group participation (i.e., anchimeric assistance) :

Since the rate of hydrolysis is much faster than that of `1^@ RX`, it follows that `E_(act)` of both steps is lower than `E_(act)` of one step `(SN^2)` mechanism for `1^@ RX`,
As the `EN` of `C` is same, we can not distinguish on the basic of inductive effect.