The relative energies of the ethane conformations are in the order

To determine the relative energies of ethane’s conformations, we need to consider their structural and energetic properties. Ethane primarily exists in two important conformations: staggered and eclipsed. A third, less commonly mentioned arrangement is referred to as skew, which falls between these two conformations in terms of torsional angle.

Analysis:

1. Staggered Conformation:
   • In this arrangement, the C-H bonds on adjacent carbons are maximally spaced apart (60° apart in torsional angle), reducing repulsive interactions between the bonding electrons.
   • As a result, the staggered conformation is the lowest energy state.
2. Eclipsed Conformation:
   • Here, the C-H bonds on adjacent carbons align directly (0° torsional angle), leading to maximum repulsion between bonding electrons.
   • This conformation is the highest energy state due to torsional strain.
3. Skew Conformation:
   • This is an intermediate state where the C-H bonds are neither fully staggered nor fully eclipsed.
   • It represents a higher energy than staggered but lower energy than eclipsed.

Correct Option:

d) staggered < skew < eclipsed