The correct stability order of the following resonance structures of $\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CHO}$ is

JEE Main · 2024 · 09 Apr 2024 · Shift 2 · General Organic Chemistry

The correct stability order of the following resonance structures of

CH_{3} - CH = CH - CHO

(A)II $>$ III $>$ I
(B)III $>$ II $>$ I✓ Correct
(C)I $>$ II $>$ III
(D)II $>$ I $>$ III

Answer: (B)

Solution

Structure III has no charge separation (all covalent bonds, non-polar), making it the most stable resonance structure. Between the two charge-separated structures, structure II places the negative charge on oxygen (more electronegative) while structure I places it on carbon (less electronegative); a negative charge is better accommodated on the more electronegative atom, so II is more stable than I.

Stability order: III > II > I.

JEE Main · 2024 · 09 Apr 2024 · Shift 2 · Single correct option

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