i. Ethanal, Propanal, Propanone, Butanone:
a. Due to inductive (+I) effect aldehydes have more electrophilic carbonyl carbon than ketones.
b. Hence aldehydes are more susceptible (to the attack of nucleophile) than ketones.
c. Hence the reactivity of propanal and ethanal is higher than that of butanone and propanone.
d. As the steric hindrance increases, reactivity decreases because the attack of the nucleophile to the carbonyl carbon becomes more difficult.
e. Hence the reactivity of propanal is lower than that of ethanal. Also the reactivity of butanone is lesser than that of propanone.
f. The increasing order of reactivity in nucleophilic addition reactions is, Butanone < Propanone < Propanal < Ethanal.
ii. Benzaldehyde, p-Tolualdehyde, p-Nitrobenzaldehyde, Acetophenone:
a. The effect of methyl group at para position of aromatic aldehydes is not significant. Hence the reactivity of benzaldehyde and p-tolualdehyde is comparable.
b. The nitro group at para position is an electron withdrawing group and makes the carbonyl carbon more electrophilic. Hence p-nitrobenzaldehyde is more reactive than benzaldehyde.
c. Aldehydes have more electrophilic carbonyl carbon than ketones. Hence aldehydes are more subceptible (to the attack of nucleophile) than ketones.
d. hence benzaldehyde is more reactive than acetophenone.
e. The increasing order of reactivity in nucleophilic addition reactions is, Acetophenone < p-Tolualdehyde , Benzaldehyde < p-Nitrobenzaldehyde.
