JEE Chemistry 2025 Question with Solution

Given: The molecule shown is $\text{CH}_3-\text{CH}(\text{OH})-\text{CH}=\text{CH}-\text{CH}_3$.

Find: The number of different stereoisomers possible.

First count all stereogenic elements in the molecule. The carbon bearing the $\text{OH}$ group is a chiral centre because it is attached to four different groups. Also, the $\text{C} = \text{C}$ double bond can show geometrical isomerism because each double-bond carbon has two different substituents.

Thus, there are two independent stereogenic elements in the molecule:

1. one chiral centre
2. one geometrical $E/Z$ double bond

So the total number of stereoisomers is

There is no internal symmetry that creates a meso form, so all four possibilities are distinct.

Therefore, the total number of different stereoisomers is $4$. The correct option is D.