Question

The correct order of relative stability of the given conformers of n-butane is

• A. II>I = III
• B. II>III>I
• C. II>I>III
• D. I = III>II

Answer 1

The Correct Option is A

To determine the relative stability of the given conformers of n-butane, we analyze the Newman projections about the central C–C bond.

Conformer II: This is the anti-conformation where the two methyl groups (CH₃) are 180° apart. It is the most stable due to minimal steric hindrance. 

Conformer I and III: Both are gauche conformations, where the methyl groups are 60° apart. These are less stable than anti due to gauche interactions (steric repulsion between bulky groups), but they are equally stable with respect to each other. 

Hence, the correct order of relative stability is: 

II > I = III