JEE Main 2025 Jan 24 Shift 2, Chemistry Q22: Stereoisomerism

JEE Main2025Jan 24, Shift 2Chemistry

The possible number of stereoisomers for 5-phenylpent-4-en-2-ol is __________.

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Solution

5-phenylpent-4-en-2-ol

Identify the stereogenic units:

C2 bears four different groups ( $- H$ , $- O H$ , $- C H_{3}$ , $- C H_{2} C H = C H P h$ ) $\Rightarrow$ one stereocentre.
The C4=C5 double bond has two different substituents on each end ( $- P h$ vs $- H$ at C5; $- C H_{2} C H O H C H_{3}$ vs $- H$ at C4) $\Rightarrow$ shows geometrical (E/Z) isomerism.

Total number of independent stereogenic units = 2, so the maximum number of stereoisomers is $2^{2} = 4$ (a pair of enantiomers for the E-alkene and a pair for the Z-alkene).

Answer: 4

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JEE Main 2025 Jan 24 Shift 2, Chemistry Q22: Stereoisomerism

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