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Organic Chemistry – Some Basic Principles and Techniques · Question 11

NEET (UG) 2022MCQEasy📈 Topic in 25% papers+4−1
1

Which compound amongst the following is not an aromatic compound?

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

Answer

(4) [figure]

Solution

As per NCERT (Hückel rule), a species is aromatic if it is cyclic and planar, has complete delocalisation of π electrons in the ring and contains (4n+2) π electrons.

⇒ (1) Cyclopentadienyl anion: every ring carbon sp2, 6 π electrons (n = 1) — aromatic.

⇒ (2) Cycloheptatrienyl (tropylium) cation: 6 π electrons (n = 1), fully conjugated — aromatic.

⇒ (3) Cyclopropenyl cation: 2 π electrons (n = 0), fully conjugated — aromatic.

⇒ (4) Cycloheptatriene: has one sp3 CH2 carbon, so π electrons are not delocalised over the whole ring — non-aromatic.

Answer: (4)

NEET (UG) 2022

Keep practising — Organic Chemistry – Some Basic Principles and Techniques

2

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
3

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)
4

Which of the following is the most stable carbocation?

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

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

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
NEET (UG) 2021
6

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
7

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
8

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
9

Which of the following carbocations is expected to be most stable?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
NEET 2018
10

Which of the following molecules represents the order of hybridisation sp2, sp2, sp, sp from left to right atoms?

  1. HC C - C CH
  2. CH2 = CH - C CH
  3. CH2 = CH - CH = CH2
  4. CH3 - CH = CH - CH3
NEET 2018
11

The correct statement regarding electrophile is

  1. electrophile is a negatively charged species and form a bond by accepting a pair of electrons from another electrophile
  2. electrophiles are generally neutral species and can form a bond by accepting a pair of electrons from a nucleophile
  3. electrophile can be either neutral or positively charged species and can form a bond by accepting a pair of electrons from a nucleophile
  4. electrophile is a negatively charged species and can form a bond by accepting a pair of electrons from a nucleophile.
NEET 2017

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