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Isomerism · Question 13

NEET 2016 (Phase 2)MCQHard📈 Topic in 0% papers+4−1
1

Which among the given molecules can exhibit tautomerism? [figure]

  1. III only
  2. Both I and III
  3. Both I and II
  4. Both II and III

Answer

(1) III only

Solution

Keto–enol tautomerism needs an α-H atom that can shift to O to form a C=C (enol).

I: both α-carbons are bridgehead carbons ⇒ a C=C at a bridgehead of this small bicyclic ring is too strained (Bredt's rule) ⇒ no enol.

II: one α-carbon is a bridgehead (no enol possible) and the other carries two Ph groups (no α-H) ⇒ no enol.

III: the α-CH2 group has α-H atoms ⇒ enol is formed ⇒ tautomerism.

∴ III only.

Answer: (1)

NEET 2016 (Phase 2)

Keep practising — Isomerism

2

The possible stereo-structures of CH3CHOHCOOH, which are optically active, are called

  1. atropisomers
  2. enantiomers
  3. mesomers
  4. diastereomers
AIPMT 2015
3

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
AIPMT 2015
4

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

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

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)
6

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
7

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
8

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)
9

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)
10

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)
11

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)

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