Explain why aldehydes are more reactive than ketones.

Explanation

Aldehydes are more reactive than ketones due to the following two reasons:
(i) Due to smaller +I-effect of one alkyl group in aldehdyes as compared to larger +I-effect of two alkyl groups, the magnitude of positive charge on the carbonyl carbon is more in aldehydes than in ketones. As a result, nucleophilic addition reactions occur more readily in aldehydes than in ketones.
(ii) Due to presence of a H-atom on the carbonyl group, aldehydes can be more easily oxidised than ketones. As a result, aldehydes act as reducing agents and thus reduce tollen' reagent, fehling's solution, etc.