Question

How many chiral carbons are there in reserpine? (an antipsychotic drug)

Answer 1

Hint: Reserpine is a drug which is mainly used for the treatment of hypertension, headache, tension and some dermatological problems.
A molecule is said to be chiral if it is not superimposable on its mirror images. Chirality often leads to optical activity in a compound, but it is not a necessary condition for optical activity.

Complete step by step answer:
There are many cases where optical activity is not because of any chiral center, but it is because of the presence of elements of chirality, like chiral axis or chiral plane. Chiral molecules have the same number of atoms but are arranged differently in space.
Molecules are chiral when they have at least one or more chiral carbon atoms. Chiral carbon is a carbon atom which is bonded to four different groups.
Consider the reserpine compound given below:

Chiral carbon is also referred to as asymmetrical carbon. Its mirror image will be a different compound. Thus the chiral carbons are given a star mark. Others are achiral. They are symmetrical and may be attached to two or more same groups.

So we can say that a total of nine chiral carbons are there in reserpine.

Note:
When the mirror image of an achiral carbon is rotated, and the structure can be aligned with each other, their mirror images are said to be achiral. Fischer projection is a two dimensional representation of a three dimensional molecule. This is more helpful for checking whether there is a chiral carbon atom or not.