The aldehydes and ketones undergo many nucleophilic reactions. Aldehydes are generally more reactive than Ketones in nucleophilic addition reactions due to steric and electronic reasons. The aldehydes and ketones undergo a number of reactions due to acidic nature of α-Hydrogen also. Aldol and cross aldol reactions occur in carbonyl compounds which contain α-Hydrogen. Aldehydes and ketones having at least one α-Hydrogen undergo reaction in dil. alkali to form β-hydroxy aldehyde or β-hydroxy ketone. This is aldol reaction. Aldol or ketol lose water to form α,β unsaturated carbonyl compounds which is called aldol condensation. Carbonyl compounds react with ammonia derivatives such as NH₂OH, NH₂NHCONH₂, 2,4 DNP to give products useful in their identification.

Ethanal undergoes nucleophilic addition reaction at faster speed than acetone, this is because of 

electrophilicity of carbon of carbonyl group is high in ethanal.

Ethanal undergoes nucleophilic addition reaction at faster speed than acetone, this is because of electrophilicity of carbon of carbonyl group is high in ethanal.

Sterically the presence of two relatively large substituents is ketones hinders the approach of nucleophile to carbonyl carbon than in aldehydes having only one such substituent. Electronically two alkyl groups reduce the positivity of the carbonyl carbon more effectively in ketones than in aldehydes.