NEET levelSingle correct optionDifficulty 1 of 3st118
Among the conformations of butane obtained by rotation about the C2-C3 bond, the most stable one is
Agauche (staggered, methyl groups 60 degrees apart)
Bpartially eclipsed (methyl groups 120 degrees apart)
Canti (staggered, methyl groups 180 degrees apart)
Dfully eclipsed (methyl groups 0 degrees apart)
Answer: C
The anti conformer has the two bulky methyl groups as far apart as possible and no torsional strain, so it is the global energy minimum. Gauche is a local minimum, about 3.8 kJ/mol higher because of methyl-methyl steric strain.