PYQSide ExamsMy practice

Isomerism · Question 15

AIPMT 2015MCQMedium📈 Topic in 12% papers+4−1
1

In an SN1 reaction on chiral centers, there is

  1. inversion more than retention leading to partial racemisation
  2. 100% retention
  3. 100% inversion
  4. 100% racemisation

Answer

(1) inversion more than retention leading to partial racemisation

Solution

In an SN1 reaction the leaving group departs first, giving a planar (sp2) carbocation.

⇒ The nucleophile can attack from both faces, so both inverted and retained products form; as per NCERT, SN1 reactions of optically active halides are accompanied by racemisation.

∵ The departing halide ion stays close to the front face for a short time (ion pair) and partly shields it, attack from the back side is slightly favoured.

∴ Inversion is more than retention ⇒ partial racemisation.

Answer: (1)

AIPMT 2015

Keep practising — Isomerism

2

The number of structural isomers possible from the molecular formula C3H9N is

  1. 5
  2. 2
  3. 3
  4. 4
AIPMT 2015
3

Given : [figure] Which of the given compounds can exhibit tautomerism?

  1. II and III
  2. I, II and III
  3. I and II
  4. I and III
AIPMT 2015 (Cancelled)
4

Which of the following compounds will undergo racemisation when solution of KOH hydrolyses? [figure]

  1. (i) and (ii)
  2. (ii) and (iv)
  3. (iv)
  4. (i) and (iv)
AIPMT 2014
5

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
NEET 2013
6

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)
7

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)
8

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)
9

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)
10

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

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2010 (Mains)
11

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

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

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