Question

Give reasons:
Propanone is less reactive than ethanal towards nucleophilic addition reactions.

Answer 1

The methyl group due to its $+I$ effect reduce the magnitude of positive charge on carbonyl carbon atom. Moreover, it also hinders the approach of the nucleophile. Since in propanone, there are two methyl groups while in acetaldehyde there is one methyl group, therefore, propanone is less reactive than acetaldehyde towards nucleophilic addition reactions.