JEE Challenger
More from Organic Chemistry - Some Basic Principles and Techniques
ChemMedAdv 2007 • Paper 2

Identifying the Least Stable Resonating Structure

Among the following, the least stable resonance structure is

Options

A
Option A Diagram 1
Correct
B
Option B Diagram 1
C
Option C Diagram 1
D
Option D Diagram 1

Topics & Concepts

Organic Chemistry - Some Basic Principles and TechniquesResonanceStability of Resonating StructuresFormal Charge

Step-by-Step Solution

Rules for Evaluating Relative Stability of Resonating Structures:

  1. Structures with complete octets for all atoms are more stable than those with incomplete octets.
  2. Structures with fewer formal charges are more stable.
  3. Negative formal charge should reside on the more electronegative atom (oxygen), and positive charge on the more electropositive atom (carbon).
  4. Structures with like charges on adjacent atoms or extensive charge separation are highly destabilized.

In Structure (A), adjacent atoms carry opposite charges in an unfavorable configuration and there is high charge separation without effective conjugation, resulting in the highest energy and lowest stability.

Correct Answer: A

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