Consider the following reactiions:

Which of the staements are correct?

Options

A. Reaction `(I)` is faster than `(II)`.
B. Reaction `(II)` is faster than `(I)`.
C. Reaction `(III)` is faster than `(IV)`.
D. Reaction `(Iv)` is faster than `(III)`.

Answer

`(a,d)`

Explanation

i. Althiough `F^(o-)` is a poor leaving group, in acidic condition, `F` froms `H-` bonding and its departure is easier. So in acidic medium, reaction `(I)` is solvolysed faster than `(II)`.
This is an example of electrophilic catalysis.
ii. The formation of `Me_(3)C - underset(Me)underset(|)overset(Me)overset(|)(C^(o+))` from `(IV)` reduces some of the streic hindreance or crowding in reactant in `(IV)`, induced by the two `(Me)` groups and the `t-Bu` on the `alpha-C` atom. This is an example of steric acceleration.
Moreover, carbocation is further stabilised by `+1` effect of two `(Me)` groups and `t-Bu` groups. So reaction `(IV)` is faster than `(III)`