Question

I. Which of the following will solvolyse faster is `SN^(-1)` and why?

II. `F^(ᶱ)` works as a good leaving group in `ArSN` reaction

even though it is a por leaving group in alipatic `SN^(-1)` and `SN^(-1)` mechanisms. Exaplin.
III. When reacts with alc. `KCN`, a mixture of ismeric products is obtained. Explain.

Answer 1

I. Compound `(A)` will solvolyse faster than `(B)`. The rate of `SN^(-1)` reaction depends on the difference in energy of the ground state abd tge transition state.
Diaxial compound `(A)` is less stable than diequatoxial compound `(B)` and thus `(A)` solvolyes faster.
II. IN `ArSN` reaction when the leaving group is `Cl, Br`, or `l`, the rate differes only by a factor of 5. This behaviour is not expected in a reaction in which the `(Ar-X)` bond is broken in the `R.D.S` . An increses in the `EN` of the leaving group such as `F^(@)` ion casuses a decrease in the electron density at the site of the attack by the muclophile, resulting in a fast reaction.
When the leaving group is `F^(@)` the rate is faster compared to the other halo group in `ArSN` reaction. This indicates that the mechanism is different from `SN^(-1)` and `SN^(-2)1` pathways.
III. It can proceed by both `SN^(-1)` and `SN^(2)`.

Two isomeric products by `SN^(-1)` mechanism are obtained.