Which of the following conformations will be the most stable?

Step 1: Identify the principle governing conformational stability For conformational stability in cyclic and acyclic systems:

• Staggered arrangements are more stable than eclipsed
• Bulky groups (like $\ce{CH3}$) should be as far apart as possible
• The anti conformation (dihedral angle = 180°) is most stable for alkanes

Step 2: Analyze conformation (a)

Conformation (a) shows the structure where the two bulky methyl groups are in anti positions relative to each other — maximally separated (dihedral angle ≈ 180°). This minimizes steric interactions.

Answer: Option (a)

Key Points to Remember:

• Anti conformation: dihedral angle = 180°, most stable for n-butane
• Gauche conformation: dihedral angle = 60°, less stable
• Eclipsed conformation: dihedral angle = 0°, least stable
• Stability: anti > gauche > partially eclipsed > fully eclipsed