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Isomerism · Question 35

AIPMT 2003MCQEasy📈 Topic in 12% papers+4−1
1

In this reaction : CH3CHO + HCN CH3CH(OH)CN HOH CH3CH(OH)COOH an asymmetric centre is generated. The acid obtained would be

  1. D-isomer
  2. L-isomer
  3. 50% D + 50% L-isomer
  4. 20% D + 80% L-isomer

Answer

(3) 50% D + 50% L-isomer

Solution

The carbonyl carbon of CH3CHO is sp2 hybridised and planar.

CN- attacks it from either face with equal probability.

Both configurations of the new chiral carbon are formed in equal amounts; hydrolysis does not affect the chiral centre.

A racemic mixture of 2-hydroxypropanoic acid (lactic acid) is obtained: 50% D + 50% L.

Answer: (3)

AIPMT 2003

Keep practising — Isomerism

2

Geometrical isomers differ in

  1. position of functional group
  2. position of atoms
  3. spatial arrangement of atoms
  4. length of carbon chain
AIPMT 2002
3

A compound of molecular formula C7H16 shows optical isomerism, compound will be

  1. 2,3-dimethylpentane
  2. 2,2-dimethylbutane
  3. 2-methylhexane
  4. none of these
AIPMT 2001
4

[figure] obtained by chlorination of n-butane will be

  1. meso form
  2. racemic mixture
  3. d-form
  4. l-form
AIPMT 2001
5

2-Butene shows geometrical isomerism due to

  1. restricted rotation about double bond
  2. free rotation about double bond
  3. free rotation about single bond
  4. chiral carbon
AIPMT 2000
6

Dihedral angle in staggered form of ethane is

  1. 0
  2. 120
  3. 60
  4. 180
AIPMT 2000

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