See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Analysis of Isomerism in the Deuterated Product **Step 1: Identify the starting compound** The product $CH_3-CHD-CHD-CH(OH)CH_3$ is obtained after $D_2/Ni$ treatment (deuteration replacing H atoms). **Step 2: Identify stereogenic centers** The molecule contains two chiral centers: - Carbon bearing $CHD$ (position 2): has groups $CH_3$, $D$, $H$, and $-CHD-CH(OH)CH_3$ - Carbon bearing $CHD$ (position 3): has groups $D$, $H$, $-CH(OH)CH_3$, and $CH_3$ Since $D$ and $H$ are isotopes with different masses, they are distinguishable groups, making both carbons stereogenic. **Step 3: Determine optical isomerism possibility** With 2 stereogenic centers, a maximum of $2^2 = 4$ stereoisomers exists (2R,2S × 3R,3S combinations). These stereoisomers are **enantiomers** and **diastereomers**, exhibiting **optical isomerism** (they rotate plane-polarized light differently). **Step 4: Determine conformation isomerism** The $C-C$ single bonds in the chain allow **free rotation** (or restricted rotation) at: - The bond between $C_2$ and $C_3$ - Other single bonds in the backbone This rotation about single bonds produces different **conformational isomers** (e.g., staggered, gauche, anti conformations). **Step 5: Conclusion** The compound exhibits: - **Optical isomerism** (due to chiral centers with $D/H$ distinction) - **Conformational isomerism** (due to rotation about single bonds) **Answer: (C) Both optical as well as conformation**