Question

How many stereoisomers does this molecule have?
(A) $2$
(B) $4$
(C) $6$
(D) $8$

Answer 1

so, first let’s know what stereoisomers are, so stereoisomers are the isomers that have the same composition of functional groups, but they differ in the orientation of these functional groups around the carbon atom.

Complete Step By Step Answer:
so, to find the number of stereoisomers a compound can have, first we need to know about the criteria that are included in the category of stereoisomers.
So, for the consideration of stereoisomers- both the geometrical isomerism and the optical isomerism is included.
For the organic compound to be optically active it should have a chiral compound.
So, now let’s calculate the number of geometrical isomers and the optical isomer.
As we can see from the given compound, that there is $1$ geometrical isomer possible for this compound
And there is one choral centre in this organic compound.
Hence, total number of stereocenter is $2$
And the formula to calculate the number of stereoisomers by calculating the number of stereo centres in the given organic compound is ${2^n}$
Where, n is the number of stereocenters in the given organic compound?
As we know from above that total number of stereocenter is $2$
So, by putting the values in the formula we will get:
${2^n}$ $= {2^2} = 4$
Hence, the number of stereoisomers is $4$
So, the correct option is B.

Note:
So, the geometrical isomerism is the isomers because of the geometry of the organic compound i.e. whether they are in Trans form or cis form.
And by the optical isomerism we refer to, the number of chiral or optically active centres present in the organic compound.