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Isomerism · Question 24

AIPMT 2010 (Mains)MCQMedium📈 Topic in 0% papers+4−1
1

Which of the following conformers for ethylene glycol is most stable?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]

Answer

(4) [figure]

Solution

Options (2) and (3) are eclipsed conformations ⇒ high torsional strain, so they are less stable.

Option (1) is the anti (staggered) form and option (4) is the gauche (staggered) form.

∵ In the gauche form the two –OH groups are close enough to form an intramolecular hydrogen bond O-H O, which more than makes up for the small gauche interaction.

∴ The gauche conformer of ethylene glycol is the most stable.

Answer: (4)

AIPMT 2010 (Mains)

Keep practising — Isomerism

2

In the following the most stable conformation of n-butane is

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2010 (Prelims)
3

Which of the following compounds will exhibit cis-trans (geometrical) isomerism?

  1. Butanol
  2. 2-Butyne
  3. 2-Butanol
  4. 2-Butene
AIPMT 2009
4

How many stereoisomers does this molecule have? CH3CH=CHCH2CHBrCH3

  1. 8
  2. 2
  3. 4
  4. 6
AIPMT 2008
5

CH3-CHCl-CH2-CH3 has a chiral centre. Which one of the following represents its R-configuration?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2007
6

If there is no rotation of plane polarised light by a compound in a specific solvent, though thought to be chiral, it may mean that

  1. the compound is certainly meso
  2. there is no compound in the solvent
  3. the compound may be a racemic mixture
  4. the compound is certainly achiral.
AIPMT 2007
7

Which of the following is not chiral?

  1. 2-Hydroxypropanoic acid
  2. 2-Butanol
  3. 2,3-Dibromopentane
  4. 3-Bromopentane
AIPMT 2006
8

The chirality of the compound [figure]

  1. R
  2. S
  3. E
  4. Z
AIPMT 2005
9

Which one of the following pairs represents stereoisomerism?

  1. Structural isomerism and geometrical isomerism
  2. Optical isomerism and geometrical isomerism
  3. Chain isomerism and rotational isomerism
  4. Linkage isomerism and geometrical isomerism.
AIPMT 2005
10

The molecular formula of diphenylmethane, [figure] is C13H12. How many structural isomers are possible when one of the hydrogens is replaced by a chlorine atom?

  1. 6
  2. 4
  3. 8
  4. 7
AIPMT 2004
11

Which of the following pairs of compounds are enantiomers?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2003

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