Question

The decreasing order of the rate of bromination of the following compounds is:
I. `PhN^(o+)Me_(3)`, II. `PhCH_(2) overset(N)Me_(3)`
III. `PhMe`, IV. `PhMe_(2)`
A. `(I) gt (II) gt (III) gt (IV)`
B. `(IV) gt (III) gt (II) gt (I)`
C. `(III) gt (IV) gt (I) gt (II)`
D. `(III) gt (IV) gt (II) gt (I)`

Answer 1

Correct Answer - `b`
Stronger the acitivating substituent `(i.e., EDG)`, faster is the rate of `SE` (bromination ) reaction. Order of `overline(e)` donating substituent:
`-overset(..)(N) Me_(2) gt - Me gt -CH_(2) overset(o+)(N) Me_(3) gt underset(("Deactivating "))(overset(o+)(N)Me_(3))`
Hence, the rate of bromination: `(IV) gt (III) gt (II) gt (I)`