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Organic Chemistry – Some Basic Principles and Techniques · Question 9

JEE Main 2026 (Online) 4th April Evening ShiftMCQHard📈 Topic in 16% papers+4−1
1

Consider the following molecules/species : [figure] The correct order of carbon-oxygen double bond length is :

  1. x > y > z
  2. y > z > x
  3. z > x > y
  4. x > z > y

Answer

(4) x > z > y

Solution

Bond length of C=O increases as its double-bond character (bond order) decreases.

(y) Acetone: no conjugation ⇒ the C=O keeps full double-bond character ⇒ shortest.

(z) Acetate ion: two equivalent resonance structures, CH3-C(=O)-O CH3-C(O )=O ⇒ each C–O bond has bond order 1.5.

(x) Tropone: in the dipolar resonance form C -O the ring becomes a tropylium ion — cyclic, planar, 6 π electrons (4n + 2, n = 1) ⇒ aromatic. This aromatic stabilisation makes the dipolar form the major contributor (tropone has a large dipole moment, ≈ 4.3 D), so its C–O bond has the greatest single-bond character ⇒ longest.

∴ Carbon-oxygen bond length: x > z > y

Answer: (4)

JEE Main 2026 (Online) 4th April Evening Shift

Keep practising — Organic Chemistry – Some Basic Principles and Techniques

2

The descending order of acidity among the following compounds is : [figure] Choose the correct answer from the options given below :

  1. B > D > E > A > C
  2. D > B > E > A > C
  3. C > A > B > D > E
  4. D > E > B > A > C
JEE Main 2026 (Online) 4th April Evening Shift
3

The strongest conjugate acid will result from:

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2026 (Online) 4th April Evening Shift
4

In IUPAC nomenclature, the correct order of decreasing priority of functional group is :

  1. -CONH2, >C=O, -CHO, -NH2, -C C-
  2. -CONH2, -COOCH3, -CHO, -NH2, -OH
  3. -CONH2, -CHO, >C=O, -NH2, -C C-
  4. -CONH2, -CHO, -CN, -NH2, -C C-
JEE Main 2026 (Online) 2nd April Morning Shift
5

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Both Statement I and Statement II are true
  2. Both Statement I and Statement II are false
  3. Statement I is true but Statement II is false
  4. Statement I is false but Statement II is true
JEE Main 2026 (Online) 2nd April Evening Shift
6

CORRECT order of stability for the following is CH2=CH-, CH3-CH2-, CH C-

  1. CH C- > CH3-CH2- > CH2=CH-
  2. CH2=CH- > CH C- > CH3-CH2-
  3. CH C- > CH2=CH- > CH3-CH2-
  4. CH3-CH2- > CH2=CH- > CH C-
JEE Main 2026 (Online) 28th January Morning Shift
7

The cyclic cations having the same number of hyperconjugation are : Choose the correct answer from the options given below :

  1. B and C Only
  2. A and B Only
  3. A and C Only
  4. A, C and D Only
JEE Main 2026 (Online) 28th January Evening Shift
8

Arrange the following alkenes in decreasing order of stability. [figure] Choose the correct answer from the options given below:

  1. III > I > II > IV
  2. III > II > I > IV
  3. I > III > II > IV
  4. I > III > IV > II
JEE Main 2026 (Online) 24th January Morning Shift
9

Arrange the following carbanions in the decreasing order of stability. I. p-Br-C6H4- CH2 II. C6H5- CH2 III. p-CH3O-C6H4- CH2 IV. p-CHO-C6H4- CH2 V. p-CH3-C6H4- CH2 Choose the correct answer from the options given below :

  1. I > II > IV > V > III
  2. IV > II > I > III > V
  3. I > IV > II > V > III
  4. IV > I > II > V > III
JEE Main 2026 (Online) 24th January Morning Shift
10

Find out the statements which are not true. Choose the correct answer from the options given below :

  1. A, D & E only
  2. A, C & D only
  3. B & D only
  4. B, D & E only
JEE Main 2026 (Online) 24th January Evening Shift
11

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below

  1. Statement I is false but Statement II is true
  2. Statement I is true but Statement II is false
  3. Both Statement I and Statement II are true
  4. Both Statement I and Statement II are false
JEE Main 2026 (Online) 23rd January Evening Shift

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