JEE Chemistry 2025 Question with Solution

Given: The compound is 5-phenylpent-4-en-2-ol.

Find: The possible number of stereoisomers.

From the structure described in the solution:

• There is one chiral center at carbon $2$.
• There is one double bond between carbons $4$ and $5$, which shows geometrical isomerism.

So, the stereochemical contributions are:

$$\text{Number from chiral center} = 2 \; (R \text{ and } S)$$ $$\text{Number from double bond} = 2 \; (\text{cis/trans or } E/Z)$$

Therefore,

$$\text{Total number of stereoisomers} = 2 \times 2 = 4$$

Hence, the possible number of stereoisomers is $4$.

Given: 5-phenylpent-4-en-2-ol contains a hydroxyl group at carbon $2$ and a double bond at carbon $4$-$5$.

Find: Total number of distinct stereoisomers.

Identify the stereogenic elements:

1. Carbon $2$ is a chiral center, so it gives two configurations: $R$ and $S$.
2. The carbon-carbon double bond between $C_4$ and $C_5$ gives two geometrical arrangements: cis/trans or $E/Z$.

Combine the possibilities:

$$2 \times 2 = 4$$

No symmetry-based reduction is indicated here, so all four combinations are distinct.

Therefore, the possible number of stereoisomers is $4$.