PYQSide ExamsMy practice

Isomerism · Question 29

AIPMT 2007MCQMedium📈 Topic in 0% papers+4−1
1

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.

Answer

(1) the compound is certainly meso

Solution

A compound containing chiral carbon atoms is expected to be optically active.

∵ In a meso compound the molecule has a plane of symmetry; the rotation caused by one half of the molecule is exactly cancelled by the other half (internal compensation).

⇒ The compound shows no rotation of plane polarised light even though it contains chiral centres, e.g. meso-tartaric acid.

As per NCERT, a racemic mixture also shows zero optical rotation, but it is an equimolar mixture of two enantiomers (external compensation), not a single compound.

∴ The single compound showing no rotation is a meso compound.

Answer: (1)

AIPMT 2007

Keep practising — Isomerism

2

Which of the following is not chiral?

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

The chirality of the compound [figure]

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

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
5

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
6

Which of the following pairs of compounds are enantiomers?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2003
7

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
AIPMT 2003
8

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
9

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
10

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

  1. meso form
  2. racemic mixture
  3. d-form
  4. l-form
AIPMT 2001
11

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

All Isomerism PYQs →

PDFDownload Isomerism PYQs as PDF Free, with answer key and a QR code to every solution — print it or study offline⬇
All NEET Chemistry chapters
Physical ChemistrySome Basic Concepts of ChemistryStructure of AtomStates of MatterThermodynamicsEquilibriumRedox ReactionsSolid StateSolutionsElectrochemistryChemical KineticsSurface Chemistry
Inorganic ChemistryClassification of Elements and Periodicity in PropertiesChemical Bonding and Molecular StructureHydrogens-Block Elementsp-Block Elements (Group 13 & 14)Environmental ChemistryGeneral Principles of Isolation of Elementsp-Block Elements (Group 15–18)d- and f-Block ElementsCoordination Compounds
Organic ChemistryOrganic Chemistry – Some Basic Principles and TechniquesIsomerismHydrocarbonsHaloalkanes and HaloarenesAlcohols, Phenols and EthersAldehydes, Ketones and Carboxylic AcidsAminesBiomoleculesPolymersChemistry in Everyday LifePrinciples Related to Practical Chemistry