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Organic Chemistry – Some Basic Principles and Techniques · Question 32

JEE Main 2025 (Online) 2nd April Morning ShiftMCQMedium📈 Topic in 3% papers+4−1
1

Consider the following compound (X) [figure] The most stable and least stable carbon radicals, respectively, produced by homolytic cleavage of corresponding C-H bond are :

  1. III, II
  2. II, IV
  3. I, IV
  4. II, I

Answer

(4) II, I

Solution

Homolysis of each marked C–H bond gives the following radicals:

I: H-C C- is formed by breaking the sp C–H bond, so the odd electron sits in an sp orbital (50% s-character, held very close to the nucleus) and cannot be delocalised least stable.

II: HC C- CH- is a propargylic radical; the odd electron is delocalised over the triple bond by resonance HC C- CH-R H C=C=CH-R most stable.

III: a 3° alkyl radical, stabilised only by hyperconjugation and +I effect.

IV: a 1° alkyl radical — less stable than the 3° radical III, but far more stable than the alkynyl radical I.

Stability order: II > III > IV > I

Most stable = II, least stable = I.

Answer: (4)

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2

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
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3

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
JEE Main 2025 (Online) 2nd April Evening Shift
4

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
5

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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6

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
JEE Main 2025 (Online) 28th January Morning Shift

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