Reactivity of `PhMgBr` with the following in the decreasing order is :
(i) `PhCHO`
(ii)
(iii)
(iv) .

Options

A. `(i) gt (iv) gt (ii) gt (iii)`
B. `(iii) gt (ii) gt (iv) gt (i)`
C. `(i) gt (iii) gt (ii) gt (iv)`
D. `(i) gt (ii) gt (iii) gt (iv)`

Answer

A

Explanation

(a) EDG (`Me` group) at `o-,m-,` and `p-positions` : At orthoposition, `ED` power of `(Me-)` group is more than `p` and `m` (due to `+ I` effect and hyperconjugation effect). `ED` power of `(Me-)` group at p-position is slightly less than the `Me` group at ortho-position (due to less `+I` effect, but equal hyperconjugative effect).
So the order of `ED` power of `(Me -)` group is `o gt p gt m- NA` is favoured by less-substituted `EDG` or more-substituted `EWG`. So, the order of reactivity of `PhMgBr` with aromatic aldehyde is

Or `(i gt iv gt ii gt iii)`.