Answer

The + l effect of the alkyl group increases in the order : Ethanal $<$ Propanal $<$ Propanone $<$ Butanone

The electron density at the carbonyl carbon increases with the increase in the $+I$ effect. As a result, the chances of attack by a nucleophile decrease. Hence, the increasing order of the reactivities of the given carbonyl compounds in nucleophilic addition reactions is:

$\text{Butanone < Propanone < Propanal < Ethanal}$

(ii)

The $+I$ effect is more in ketone than in aldehyde. Hence, acetophenone is the least reactive in nucleophilic addition reactions. Among aldehydes, the $+I$ effect is the highest in $p$-tolualdehyde because of the presence of the electrondonating - ${CH_3}$ group and the lowest in $p$-nitrobezaldehyde because of the presence of the electron-withdrawing ${NO_2}$ group. Hence, the increasing order of the reactivities of the given compounds is:

$\text{Acetophenone < p-tolualdehyde < Benzaldehyde < p-Nitrobenzaldehyde} $

Answer