Arrange the following compounds in increasing order of their reactivity towards HCN.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (C), (D), (B), (A)
HCN adds to carbonyl compounds via nucleophilic addition.
Reactivity depends on: • Steric hindrance • +I effect of alkyl groups
More bulky alkyl groups → Less reactivity
Aldehydes react faster than ketones because: • Less steric hindrance • Less electron donation
Reactivity order: Highly bulky ketone < Moderately bulky ketone < Simple ketone < Aldehyde
Identify the compounds
-
(A) CH₃CHO (acetaldehyde) → aldehyde → least steric hindrance → most reactive
-
(B) CH₃COCH₃ (acetone) → ketone with two methyl groups.More hindered than aldehyde
-
(D) Ketone with one tert-butyl group → Moderately bulky ketone → Between simple and highly bulky
-
(C) Ketone with two tert-butyl groups → Highly bulky ketone → Maximum steric hindrance → Least reactive
Increasing order of reactivity toward HCN
Most steric hindrance → least reactive:
C < D < B < A