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Isomerism

AIPMT 2000MCQEasyNot asked in last 5 yrs+4−1
Ques. 1AIPMT 2000

Dihedral angle in staggered form of ethane is

  1. 0
  2. 120
  3. 60
  4. 180

Answer

(3) 60

Solution

In the Newman projection of the staggered conformation, the three C–H bonds of the rear carbon lie exactly midway between the three C–H bonds of the front carbon:

[figure]

∵ The front bonds are 120 apart and each rear bond bisects the angle between two front bonds.

⇒ Dihedral (torsional) angle between the nearest C–H bonds = 120 2 = 60

(In the eclipsed form the dihedral angle is 0 .)

Answer: (3)

Keep practising — Isomerism

Ques. 2NEET (UG) 2026

Match List I with List II :

  1. A-I, B-III, C-II, D-IV
  2. A-II, B-IV, C-III, D-I
  3. A-III, B-I, C-IV, D-II
  4. A-III, B-I, C-II, D-IV
Ques. 3NEET (UG) 2026

The pair of molecules that are metamers among the following is :

  1. CH3OCH2CH2CH3 and CH3CH2OCH2CH3
  2. CH3CH2CH2OH and CH3-CH(OH)-CH3
  3. CH3CH2CH2CH2CH3 and (CH3)2CHCH2CH3
  4. [figure] and [figure]
Ques. 4NEET (UG) 2025

How many products (including stereoisomers) are expected from monochlorination of the following compound? [figure]

  1. 5
  2. 6
  3. 2
  4. 3
Ques. 5NEET (UG) 2025

Total number of possible isomers (both structural as well as stereoisomers) of cyclic ethers of molecular formula C4H8O is :

  1. 10
  2. 11
  3. 6
  4. 8
Ques. 6NEET (UG) 2025

Which one of the following compounds can exist as cis-trans isomers?

  1. 1,1-Dimethylcyclopropane
  2. 1,2-Dimethylcyclohexane
  3. Pent-1-ene
  4. 2-Methylhex-2-ene
Ques. 7NEET (UG) 2022

The incorrect statement regarding chirality is

  1. SN1 reaction yields 1 : 1 mixture of both enantiomers
  2. The product obtained by SN2 reaction of haloalkane having chirality at the reactive site shows inversion of configuration
  3. Enantiomers are superimposable mirror images on each other
  4. A racemic mixture shows zero optical rotation
Ques. 8NEET (UG) 2021

The compound which shows metamerism is :

  1. C4H10O
  2. C5H12
  3. C3H8O
  4. C3H6O
Ques. 9NEET (UG) 2021

Dihedral angle of least stable conformer of ethane is :

  1. 0
  2. 120
  3. 180
  4. 60
Ques. 10NEET 2017

With respect to the conformers of ethane, which of the following statements is true?

  1. Bond angle changes but bond length remains same.
  2. Both bond angle and bond length change.
  3. Both bond angle and bond length remain same.
  4. Bond angle remains same but bond length changes.
Ques. 11NEET 2016 (Phase 1)

Which of the following biphenyls is optically active ?

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

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