Which of the following will have the least hindered rotation about carbon-carbon bonds?

Options

A. Ethyne
B. Ethene
C. Ethane
D. Hexachloroethane

Answer

C

Explanation

The rotation about carbon-carbon bond is least hindered when it is a single bond. Ethene has a double bond and ethyne a triple bond. Only ethane and hexachloroethane have a carbon-carbon single bond. However, the large chlorine atom in hexachloroethane present steric hindrance in contrast to the much smaller hydrogen atoms in ethane.