Arrange the following compounds in increasing order towards Nucleophilic addition reactions:
(A) Propanal
(B) Benzaldehyde
(C) Acetone
(D) Di-tert-butyl ketone
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (D), (C), (B), (A)
In nucleophilic addition the nucleophile attacks the carbonyl carbon. Two factors decide how easily this happens:
Steric factor: groups on the carbonyl carbon crowd the approaching nucleophile. An aldehyde has one group and a hydrogen; a ketone has two groups, and bulky ones such as tert-butyl hinder the attack most. On this factor alone: propanal, benzaldehyde > acetone > di-tert-butyl ketone.
Electronic factor: alkyl groups release electrons and reduce the positive charge on the carbonyl carbon; in benzaldehyde the benzene ring also feeds electrons into the C=O group by resonance. On this factor alone: propanal > benzaldehyde, and aldehydes > ketones.
Matching the labels to the compounds:
(A) Propanal: aliphatic aldehyde, one small alkyl group
(B) Benzaldehyde: aromatic aldehyde, carbonyl carbon less electrophilic because of resonance
(C) Acetone: ketone with two methyl groups
(D) Di-tert-butyl ketone: ketone with two very bulky groups
Shortcut: Di-tert-butyl ketone, with two bulky groups, must be the least reactive; only Option (1) starts with (D).
NCERT (2026-27 edition):
Reactivity
