Give the decreasing order of reactivity of the following towards hydrolysis (or nucleophilic acyl substitution) :
(i) (I) `PhCOOMe`
(II)
(II)
(IV)
(ii) (I) `PhCOCl`
(II)
(iii) (I) `PhCOCl`
(III) `Me_2 CHCOCl`
(IV) `Me_3 C-COCl`.
(b) Give the decreasing order of transacylation reactivities and nucleophilic acyl substitution reactivities fo the following :
(I) `MeCOCl`
(II) `MeCON_3`
(III) `(MeCO)_2 O`
(IV) `MeCOOMe`
(V) `MeCONH_2`.

Explanation

(a) Ease of hydrolysis or nucleophilic acyl substitution is more favoured by more `EWG`.
`EW` order : `(-NO) [ (-I) and (-R)`
`ED` order : `(-Ome)[(+R) and (-I)] gt (-Me) [(+I)` and three `H.C` structures].
(i) So the decreasing order is `(II) gt (I) gt (III) gt (IV)`.
(ii) `EW` order : `(O-NO_2) [(-I) and (-R), but (-I) at o gt m gt p )] gt (p- NO_2) [(-I) and (-R)] gt (m-NO_2) [(only (-I)]`.
So the decreasing order is : `(IV) gt (II) gt (III) gt (I)`.
(iii) Aliphatic acid derivaties are more reactive than aromatic acid derivaties (like `N.A` reaction). Comparision between `(II)` and `(III)` :
`(II)` and `(III)` both have two `(R)` groups attached to `(C=O)` group. In `(II)`, the `R` groups are sides of the ring and are 'tied back' and this arrangement permits a more facile approach by nucleophile `(Nu^(Ө))` than in `(III)`.
So the decreasing order of reactivity is :
`(II) gt (III) gt (IV) gt (I)`.
(b) The decreasing order of reaction is :
`(I) gt (II) gt (III) gt (IV) gt (V)`.