Question

Rank the following carbonyl-containing compounds in order of reactivity towards nucleophilic attack. Most Reactive to least reactive. 3-methylpentanoyl chloride, acetic anhydride, hexyl propanoate, N,N-diphenylethanamide, butanedial, and propanone.

Answer 1

First of all carbonyp compounds (wldehyald and ketones) are more reactive than acid derivatives (acid chloride, anhydride, ester,amide ).

Since we need more positive charge on carbonyl carbon for Nucleophilic attack.

In acid derivatives lone pair of electrons on hetero atoms (N,O, and halogen) decreases the positive charge on carbonyl carbon.

Reactivity of acid derivatives: acid chloride>anhydride>ester>amide.

Low electronegativuty of N in amides easily donate and decreases the reactivity, hence amide is least reactive.

And between carbonyl compounds, aldehyde .is more reactive than ketone since alkyl group (+I group) decreases the positive charge on carbonyl carbon of ketone.

Hence final order is as follows

Butane dial>propanone>3-methylpentanoyl chloride> acetic anhydride>hexylketone> N,N-diphenylethanamide.