Question

Which of the following compounds produces an optically inactive compound on hydrogenation?

Answer 1

• Hydrogenation is the addition of ${\mathrm{H}}_2$ to any unsaturated chemical compound.
• Optically inactive compounds are those which cannot rotate the plane of polarised light.
• A tetrahedral carbon atom that is bonded to four different groups is called a chiral centre or an asymmetric centre. Molecules containing only 1 chiral centre are called chiral molecules and they are optically active.
• Molecules in which all the carbon atoms are attached to two or more groups that are identical do not have any chiral centres. Such molecules are said to be achiral. All achiral molecules are optically inactive.

Explanation of correct option:

Option (C)
The hydrogenation reaction for this molecule is shown below

The product obtained has no chiral centres and therefore, it is achiral and optically inactive.

Explanation of incorrect options

Option (A): Hydrogenation of this molecule results in a molecule with a single chiral centre. Thus, the molecule is chiral and optically active.

Option (B): Hydrogenation of this molecule results in a molecule with a single chiral centre. Thus, the molecule is chiral and optically active.

Option (D: Hydrogenation of this molecule results in a molecule with a single chiral centre. Thus, the molecule is chiral and optically active.

Hence, option (C) is the correct answer.