See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Identifying Non-Identical Species **Option (A):** - First structure: $CH_3$ groups at top and bottom, $H$ and $OH$ on sides (vertical arrangement) - Second structure: $OH$ at top, $H$ and $CH_3$ on sides, $CH_3$ at bottom These are **enantiomers** (mirror images that are non-superimposable) because they represent opposite stereochemistry at the chiral center. --- **Why other options are identical:** **(B)** Both structures have the same four groups ($CH_3$, $OH$, $H$, $C_2H_5$) around the chiral center in identical stereochemical arrangement → **identical compounds** **(C)** Both are alkenes with the same substitution pattern ($Cl$ and $Br$ on one carbon; two $CH_3$ groups on the other) → **identical (cis/trans isomers can have same functional groups)** **(D)** Both have benzene ring with $Cl$, $Br$, and $CH_3$ substituents in ortho positions → **identical compounds** (just rotated differently in 2D representation) --- **Answer: (A)** represents non-identical species because they are **stereoisomers (enantiomers)** with opposite configurations at the stereogenic center.