Question

The possible number of stereoisomers for 5-phenylpent-4-en-2-ol is:________________

Hint:

For molecules with two chiral centers, use the $2^n$ rule to calculate the maximum number of stereoisomers, where $n$ is the number of chiral centers. Then check for symmetry to reduce the number of distinct stereoisomers.

Answer 1

Step 1: The given compound is $5$-phenylpent-4-en-2-ol. This is a compound with one chiral center at $C_2$ and one at $C_4$, which means it can form stereoisomers.

Step 2: Since the structure is of an alkene (with a double bond) at position 4, and the hydroxyl group ($OH$) at position 2, the molecule can form cis and trans stereoisomers depending on the orientation of the substituents about the double bond.

Step 3: There are two chiral centers in the molecule. For each chiral center, there are two possibilities (R or S), leading to a total of $2^2 = 4$ stereoisomers. However, the molecule also has a plane of symmetry due to the phenyl group, which reduces the total number of stereoisomers.

Step 4: Hence, the molecule has only 2 stereoisomers.