9701 MCQ Solution 70

Question 70: [Organic > Carbonyl Compounds]

The product of the reaction between propanone and hydrogen cyanide is hydrolysed under acidic conditions.

What is the formula of the final product?

A CH₃CH(OH)CO₂H

B CH₃CH₂CH₂CO₂H

C (CH₃)₂CHCONH₂

D (CH₃)₂C(OH)CO₂H

Reference: Past Exam Paper –June 2003 Paper 1 Q30

Solution 70:

Answer: D.

First observe the formula for propanone: (CH₃)₂C=O. The reactants undergo nucleophilic addition. The CN from HCN bonds with the central carbon atom, breaking the double bond with oxygen into a single bond. The oxygen has a polar charge attracting the remaining H atom from HCN, to form an alcohol group. Under acidic conditions the CN group is oxidised into a carboxylic acid. This is best shown by the product in option D.