Arrange the following compounds in increasing order of their reactivity in nucleophilic in nucleophili addition reaction:
(i) Ethanal, propanal, propanone, Butanone.
(ii) Benzaldehyde, p−Toluahyde, p−Nitrobenzeldehyde, Acetophenone.
(i) Ethanal, propanal, propanone, Butanone.
(ii) Benzaldehyde, p−Toluahyde, p−Nitrobenzeldehyde, Acetophenone.
(i)The +I 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:
Butanone < Propanone < Propanal < Ethanal
(ii)The +I effect is more in ketone than an 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 electron-donating -CH3group and the lowest in p-nitrobenzaldehyde because of the presence of the electron-withdrawing -NO2group. Hence, the increasing order of the reactivities of the given compounds is:
Acetophenone < p-tolualdehyde < Benzaldehyde< p-Nitrobenzaldehyde
(i)The +I 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:
Butanone < Propanone < Propanal < Ethanal
(ii)The +I effect is more in ketone than an 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 electron-donating -CH3group and the lowest in p-nitrobenzaldehyde because of the presence of the electron-withdrawing -NO2group. Hence, the increasing order of the reactivities of the given compounds is:
Acetophenone < p-tolualdehyde < Benzaldehyde< p-Nitrobenzaldehyde
