Statement I: There are several conformers for n-butane. Out of those conformers, 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:X and Y structures
(A)Both Statement I and Statement II are false
(B)Statement I is false but Statement II is true
(C)Statement I is true but Statement II is false
(D)Both Statement I and Statement II are true✓ Correct
Answer: (D)
Solution
Statement I identifies the least and most stable conformers of n-butane. Rotation about the central C-C bond gives several conformers: the fully eclipsed form, in which the two methyl groups eclipse each other, has the greatest steric and torsional strain and is least stable, while the anti conformer, with the methyl groups 180∘ apart (the staggered arrangement shown), has minimum strain and is most stable, so Statement I is correct. Statement II concerns the change from the eclipsed form to the anti form: as the dihedral angle increases from the eclipsed arrangement, the overlap of adjacent bonding electrons is relieved and the torsional strain decreases, so Statement II is also correct. Both statements are true.
JEE Main · 2026 · 24 Jan 2026 · Shift 2 · Single correct option
