Given below are two statements:
Statement I: There are several conformers for n-butane. Out of those conformers,

is the least stable and most stable conformer is

Statement II: As the dihedral angle increases, torsional strain decreases from (X) to (Y).
In the light of the above statements, choose the correct answer from the options given below

• Statement I:
  • Conformer (X) is the fully eclipsed conformation (dihedral angle = $$0^\circ$$) where the bulky $$-\text{CH}_3$$ groups are aligned directly behind each other. It has maximum steric and torsional strain, making it the least stable.
  • Conformer (Y) is the anti-staggered conformation (dihedral angle = $$180^\circ$$) where the $$-\text{CH}_3$$ groups are as far apart as possible. It has minimal steric hindrance and zero torsional strain, making it the most stable.
  • Thus, Statement I is True.
• Statement II:
  • As we rotate from the fully eclipsed form (X) (dihedral angle = $$0^\circ$$) to the anti-staggered form (Y) (dihedral angle = $$180^\circ$$), the alignment of bonding electron pairs transitions from fully overlapping to fully staggered. Hence, the overall torsional strain decreases.
  • Thus, Statement II is True.

Conclusion:

Both statements accurately describe the stability and torsional strain changes in the conformers of n-butane.

Answer: Option B — Both Statement I and Statement II are true