PYQSide ExamsMy practice

Isomerism · Question 19

NEET 2013MCQMedium📈 Topic in 0% papers+4−1
1

The order of stability of the following tautomeric compounds is [figure]

  1. II > I > III
  2. II > III > I
  3. I > II > III
  4. III > II > I

Answer

(4) III > II > I

Solution

I and III are enol forms and II is the keto form (pentane-2,4-dione) of the same compound.

∵ In I the C=C bond is isolated; it is not conjugated with C=O and there is no intramolecular H-bond.

⇒ I is the least stable form.

∵ In III the C=C bond is conjugated with C=O, and the enolic –OH forms an intramolecular hydrogen bond with the C=O oxygen (a stable six-membered ring).

⇒ III is more stable than the keto form II (pentane-2,4-dione exists mainly in the enol form).

∴ Order of stability: III > II > I

Answer: (4)

NEET 2013

Keep practising — Isomerism

2

Given: [figure] I and II are

  1. identical
  2. a pair of conformers
  3. a pair of geometrical isomers
  4. a pair of optical isomers
NEET 2013 (Karnataka)
3

Number of isomeric alcohols of molecular formula C6H14O which give positive iodoform test is

  1. three
  2. four
  3. five
  4. two
NEET 2013 (Karnataka)
4

Which of the following acids does not exhibit optical isomerism?

  1. Maleic acid
  2. -amino acids
  3. Lactic acid
  4. Tartaric acid
AIPMT 2012 (Prelims)
5

The IUPAC name of the following compound is [figure]

  1. trans-2-chloro-3-iodo-2-pentene
  2. cis-3-iodo-4-chloro-3-pentene
  3. trans-3-iodo-4-chloro-3-pentene
  4. cis-2-chloro-3-iodo-2-pentene
AIPMT 2011 (Mains)
6

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

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2010 (Mains)
7

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

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2010 (Prelims)
8

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

  1. Butanol
  2. 2-Butyne
  3. 2-Butanol
  4. 2-Butene
AIPMT 2009
9

How many stereoisomers does this molecule have? CH3CH=CHCH2CHBrCH3

  1. 8
  2. 2
  3. 4
  4. 6
AIPMT 2008
10

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
11

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

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