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JEE Main 9 April 2024, Shift 2, Chemistry Q73

Question 73 of 90 in this shift, Chemistry question 13 of 30, Section A.

The correct stability order of the following resonance structures of

\mathrm{CH_3-CH=CH-CHO}

is I:

\mathrm{CH_3-\overset{\ominus}{C}H-CH=CH-\ddot{O}:^{\oplus}}

(carbanion on the carbon next to CH

_3

, with

\mathrm{C=O}

carbon double bonded to the middle carbon and the oxygen carrying a positive charge) II:

\mathrm{CH_3-\overset{\oplus}{C}H-CH=CH-\ddot{O}:^{\ominus}}

(carbocation on the carbon next to CH

_3

, oxygen carrying a negative charge) III:

\mathrm{CH_3-CH=CH-CH=O}

The figure, in words

Three resonance structures of crotonaldehyde (CH3-CH=CH-CHO) drawn with ↔ arrows. I: CH3-CH(−)-CH=C(H)-O(+) (negative charge on the carbon next to CH3, oxygen with lone pairs and a + charge, drawn as :O:⊕). II: CH3-CH(+)-CH=C(H)-O(−) (positive charge on the carbon next to CH3, oxygen drawn :O:⊖). III: CH3-CH=CH-C(H)=O (neutral).

(1)III > II > IOfficial answer
(2)I > II > III
(3)II > III > I
(4)II > I > III

Official answer

Option 1

NTA final key.

Chapter: Organic Chemistry: Some Basic Principles and Techniques
Topic: Resonance and Hyperconjugation
Idea tested: Relative Stability

JEE Main 9 April 2024, Shift 2, Chemistry Q73

Same idea in other shifts