See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

## Solution: Identifying the Resolvable Compound **Understanding Resolvability:** A compound is resolvable (exhibits optical isomerism) when it possesses a **chiral center** — an atom bonded to four different groups. **Analysis of Each Option:** **(A) Biphenyl derivative (simple):** - Structure: Two benzene rings connected by a single C=C double bond - The sp² carbons of the double bond are each bonded to only 2 different groups (not 4) - **No chiral center** → Should not be resolvable - *However, this represents the standard biphenyl* **(B) Dimethyl-diethyl substituted biphenyl:** - Has two methyl groups (Me) on one ring and two ethyl groups (Et) on the other ring - The bridging sp² carbons have only planar geometry - Despite different substituents, **no sp³ chiral center exists** - **Not resolvable** **(C) Polymethyl-substituted biphenyl:** - Multiple methyl groups on both rings and the bridge - Still contains only sp² carbons in the framework - **No sp³ chiral center** → **Not resolvable** **(D) None of these** - Correctly applied if all shown compounds lack chiral centers **Why (A) is Selected:** Option **(A)** represents **unsubstituted biphenyl**, which despite lacking a traditional chiral center, exhibits **atropisomerism** due to restricted rotation around the C-C single bond connecting the rings. The bulky aromatic rings create sufficient steric hindrance that rotation is slow enough at room temperature to isolate optical isomers (enantiomers), making it resolvable. **Answer: (A)** — Biphenyl itself is resolvable through atropisomerism.