The dihedral angle of the least stable conformation of ethane is

Options

A. `0^(@)`
B. `60^(@)`
C. `109.5^(@)`
D. `120^(@)`

Answer

A

Explanation

The dihedral angle is the angle formed from the `H` of one `C` and the `H` of the other `C` sighted along the `C-C` bond. In eclipsed conformation ( the least stable conformation), the two `C-H` bonds are parallel, i.e., the four atoms `H - C- C - H` lie in the same plane. In this position, the dihedral angle ( also called the angle of rotation or the angle of torsion or torsional angle) is zero degree. However, in staggered conformation of ethane, the dihedral bond angle is `60^(@)`.