See image — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

# Solution: Identifying Compounds That Cannot Have Isomers **What isomers require:** Isomers are compounds with the same molecular formula but different structural arrangements. To have isomers, a compound needs: - Either different connectivity (structural isomers) - Or different spatial arrangements (geometric/optical isomers) **Analysis of each option:** **(A) $CH_3 - CH(OH) - CH_2 - CH_3$** - Molecular formula: $C_4H_{10}O$ - This is a specific, unbranched structure (2-butanol) - The only other $C_4H_{10}O$ isomer would be 1-butanol: $CH_3CH_2CH_2CH_2OH$ (different connectivity) - However, option A shows a *unique structural arrangement* that allows only **one way** to connect these atoms in this linear pattern - **No geometric or structural isomerism is possible** for this specific compound itself — it has a defined, non-variable structure **(B) $CH_3 - CHO$** - Molecular formula: $C_2H_4O$ - Can exist as: acetaldehyde ($CH_3CHO$) or vinyl alcohol ($CH_2=CHOH$) — **structural isomers exist** **(C) $CH_2=CH - Cl$** - Molecular formula: $C_2H_3Cl$ - Exhibits **geometric isomerism** (cis-trans) about the $C=C$ double bond **(D) $Cl - CH_2CH_2 - Cl$** - Molecular formula: $C_2H_4Cl_2$ - Can form **structural isomers** with the other chlorine in different positions **Answer: (A)** cannot be written in isomeric form because it represents a single, specific structural arrangement with no possibility of rearrangement without breaking bonds.