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Organic Chemistry – Some Basic Principles and Techniques · Question 33

JEE Main 2025 (Online) 2nd April Morning ShiftMCQMedium📈 Topic in 6% papers+4−1
1

Designate whether each of the following compounds is aromatic or not aromatic. [figure]

  1. a, c, d, e, h aromatic and b, f, g not aromatic
  2. b, e, f, g aromatic and a, c, d, h not aromatic
  3. a, b, c, d aromatic and e, f, g, h not aromatic
  4. e, g aromatic and a, b, c, d, f, h not aromatic

Answer

(1) a, c, d, e, h aromatic and b, f, g not aromatic

Solution

A species is aromatic if it is cyclic, planar, fully conjugated and has (4n+2) π electrons (Hückel rule).

(a) cyclopentadienyl anion: 4 π + lone pair in conjugation = 6 π (n = 1) aromatic

(b) cyclopentadienyl cation: 4 π (4n) not aromatic (antiaromatic)

(c) cyclobutadienyl dication: 2 π (n = 0) aromatic

(d) cyclobutadienyl dianion: 2 π + 4 electrons of the two carbanions = 6 π aromatic

(e) cycloheptatrienyl (tropylium) cation: 6 π aromatic

(f) cyclooctatetraene: 8 π, tub-shaped (non-planar) not aromatic

(g) cyclobutadiene: 4 π not aromatic (antiaromatic)

(h) cyclopropenyl cation: 2 π aromatic

a, c, d, e, h are aromatic and b, f, g are not aromatic.

Answer: (1)

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2

In 3,3-dimethylhex-1-en-4-yne, there are sp3, sp2 and sp hybridised carbon atoms respectively.

  1. 4, 2, 2
  2. 2, 4, 2
  3. 3, 3, 2
  4. 2, 2, 4
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3

Match List - I with List - II. Choose the correct answer from the options given below :

  1. (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
  2. (A)-(II), (B)-(III), (C)-(I), (D)-(IV)
  3. (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
  4. (A)-(III), (B)-(II), (C)-(I), (D)-(IV)
JEE Main 2025 (Online) 29th January Morning Shift
4

Total number of nucleophiles from the following is : NH3, PhSH, (H3C)2S, H2C=CH2, OH, H3O , (CH3)2 CO, [figure]

  1. 4
  2. 6
  3. 5
  4. 7
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5

The correct order of stability of following carbocations is : [figure]

  1. A > B > C > D
  2. C > B > A > D
  3. B > C > A > D
  4. C > A > B > D
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