Ques. 1AIPMT 2003
In this reaction : CH3CHO + HCN CH3CH(OH)CN HOH CH3CH(OH)COOH an asymmetric centre is generated. The acid obtained would be
- D-isomer
- L-isomer
- 50% D + 50% L-isomer
- 20% D + 80% L-isomer
Answer
(3) 50% D + 50% L-isomer
Solution
The carbonyl carbon of CH3CHO is sp2 hybridised and planar, so CN- attacks it from either face with equal probability.
Hence both configurations of the new chiral carbon are formed in equal amounts, and hydrolysis does not affect the chiral centre.
A racemic mixture of 2-hydroxypropanoic acid (lactic acid) is obtained: 50% D + 50% L.
Answer: (3)