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Organic Chemistry – Some Basic Principles and Techniques · Question 8

RE-NEET (UG) 2024MCQEasy📈 Topic in 12% papers+4−1
1

Methyl group attached to a positively charged carbon atom stabilizes the carbocation due to

  1. -I inductive effect
  2. electromeric effect
  3. hyperconjugation
  4. mesomeric effect

Answer

(3) hyperconjugation

Solution

The σ electrons of the α C–H bonds of the methyl group delocalise into the empty p orbital of the positively charged carbon (σ–p overlap, no-bond resonance). This hyperconjugation spreads the positive charge and stabilises the carbocation. (A methyl group shows a +I effect, not −I.)

Answer: (3)

RE-NEET (UG) 2024

Keep practising — Organic Chemistry – Some Basic Principles and Techniques

2

The number of bonds, bonds and lone pair of electrons in pyridine, respectively are:

  1. 12, 3, 0
  2. 11, 3, 1
  3. 12, 2, 1
  4. 11, 2, 0
NEET (UG) 2023
3

Consider the following compounds/species: [figure] The number of compounds/species which obey Hückel's rule is .

  1. 6
  2. 2
  3. 5
  4. 4
NEET (UG) 2023
4

Which compound amongst the following is not an aromatic compound?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
NEET (UG) 2022
5

The correct IUPAC name of the following compound is [figure]

  1. 1-bromo-5-chloro-4-methylhexan-3-ol
  2. 6-bromo-2-chloro-4-methylhexan-4-ol
  3. 1-bromo-4-methyl-5-chlorohexan-3-ol
  4. 6-bromo-4-methyl-2-chlorohexan-4-ol
NEET (UG) 2022
6

What is the hybridization shown by C1 and C2 carbons, respectively in the given compound? OHC- 1CH=CH- 2CH2COOCH3

  1. sp3 and sp3
  2. sp2 and sp3
  3. sp2 and sp2
  4. sp3 and sp2
NEET (UG) 2022 (Phase 2)
7

Which of the following is the most stable carbocation?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
NEET (UG) 2022 (Phase 2)
8

The correct structure of 2, 6-dimethyl-dec-4-ene is

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
NEET (UG) 2021
9

A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of which of the following?

  1. +R effect of -CH3 groups
  2. -R effect of -CH3 groups
  3. Hyperconjugation
  4. -I effect of -CH3 groups
NEET (UG) 2020
10

The number of sigma ( ) and pi ( ) bonds in pent-3-en-1-yne is -

  1. 11 bonds and 2 bonds
  2. 13 bonds and no bonds
  3. 10 bonds and 3 bonds
  4. 8 bonds and 5 bonds
NEET (UG) 2019
11

Which of the following is correct with respect to -I effect of the substituents? (R = alkyl)

  1. -NH2 < -OR < -F
  2. -NR2 < -OR < -F
  3. -NH2 > -OR > -F
  4. -NR2 > -OR > -F
NEET 2018

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