Question

Which of the following is optically active?
A. Butan-2-ol
B. 3-methyl butan-2-ol
C. Both of the above
D. None of the above

Answer 1

The organic compounds which have a chiral carbon in its structure are called optically active molecules. A carbon which contains four different groups attached to it in a molecule is called chiral carbon.

Complete answer:
- In the question it is asked which of the molecules are going to exhibit optical activity among the given options.
- To know whether the given molecules are optically active or not we should know the structures of the molecules given in the options.
- Coming to the option A, Butan-2-ol. The structure of Butan-2-ol is as follows.

- From the above structure we can say that the butan-2-ol contains one chiral carbon and it is labeled with a star mark in the above structure.
- Therefore butan-2-ol is optically active.
- Coming to the option B, 3-methyl butan-2-ol. The structure of 3-methyl butan-2-ol is as follows.

- From the above structure we can say that the 3-methyl butan-2-ol contains one chiral carbon and it is labeled with a star mark in the above structure.
- Therefore 3-methyl butan-2-ol is optically active.
- Therefore both the molecules in option A and option B are optically active.

The correct answer is option “C” .

Note: To get the property of the optical activity the organic molecules should contain a chiral carbon. The optical activity of the organic compounds is going to be measured by using a polarimeter. Organic compounds with chiral carbons exist in two forms, d and l forms.