c
In acyl compounds (i.e. acyl chloride, acid anhydride, ester and amide) RCO-group is same, thus reactivity depends upon the nature of group \(Z\) (i.e. \(\left.\mathrm{Cl^-}, \mathrm{RCOO}^{-}, \mathrm{R}^{\prime} \mathrm{O}^{-}, \mathrm{NH}_{2}^{-}, \text {etc. }\right)\)

If group \(Z\) is a weak base, then it is a strong leaving agent and its reactivity towards nucleophilic substitution is high. The order of basic nature of \(Z\) groups is

\(C l^{-} < R C O O^{-} < R^{\prime} O^{-} > N H_{2}^{-}\)

Thus, order of reactivity is

\(R C O C l >(R C O)_{2} O > R C O O R^{\prime} >R C O N H_{2}\)

\(Acyl chloride > Acid anhydride > Ester > Amide\)