Question

In Baeyer strain theory, which cycloalkane is more stable?

• A. Cyclopropane
• B. Cyclobutane
• C. Cyclopentane
• D. Cyclooctane

Hint:

Remember: Cyclopentane has minimal angle strain and is considered most stable according to Baeyer's angle strain theory — important for understanding ring stability in GPAT.

Answer 1

The Correct Option is C

- Baeyer Strain Theory (proposed by Adolf von Baeyer) explains the relative stability of cycloalkanes based on angle strain. According to this theory, the most stable ring systems are those in which the bond angles are closest to the tetrahedral angle of \( 109.5^\circ \).
- The ideal bond angle in a tetrahedral molecule is \( 109.5^\circ \), and any deviation from this causes angle strain.
Let’s analyze the ring strain in each option:
- (A) Cyclopropane: Bond angle = \( 60^\circ \) → High strain
- (B) Cyclobutane: Bond angle = \( 90^\circ \) → Considerable strain
- (C) Cyclopentane: Bond angle = \( 108^\circ \) → Closest to 109.5° → Least strain and most stable
- (D) Cyclooctane: Angle strain is reduced, but suffers from torsional strain due to its flexible ring, making it less stable than cyclopentane
- Hence, Cyclopentane is considered the most stable cycloalkane as per Baeyer strain theory.