Which one of the following compounds can exist as cis-trans isomers?
(1) 1,2-Dimethylcyclohexane
(2)

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Question

Which one of the following compounds can exist as cis-trans isomers?
(1) 1,2-Dimethylcyclohexane
(2) Pent-1-ene
(3) 2-Methylhex-2-ene
(4) 1,1-Dimethylcyclopropane

Accepted Answer

Correct Answer: A — 1,2-DimethylcyclohexaneStep-by-step Solution:Condition for cis-trans isomerism: Restricted rotation + each carbon at the restricted site must bear two different substituents.A. 1,2-Dimethylcyclohexane ✓: Ring restricts rotation. C1 has –CH₃ and –H; C2 has –CH₃ and –H (both different). Methyls can be cis (same face) or trans (opposite faces). → Cis-trans isomers exist.B. Pent-1-ene ✗: C1 (=CH₂) has two identical H atoms → condition not satisfied.C. 2-Methylhex-2-ene ✗: C2 of the double bond has two methyl groups (identical) → no cis-trans isomerism.D. 1,1-Dimethylcyclopropane ✗: Both methyls on the same carbon (C1 has two identical –CH₃ groups) → condition not satisfied.Key Concepts:Cis-trans (geometrical) isomerism conditions: (1) Restricted rotation (double bond or ring). (2) Each sp² carbon (or ring carbon) must have two different groups.Cis = same side; Trans = opposite sides of the reference plane.

Which one of the following compounds can exist as cis-trans isomers? (1) 1,2-Dimethylcyclohexane (2) Pent-1-ene (3) 2-Methylhex-2-ene (4) 1,1-Dimethylcyclopropane

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Which one of the following compounds can exist as cis-trans isomers? (1) 1,2-Dimethylcyclohexane (2) Pent-1-ene (3) 2-Methylhex-2-ene (4) 1,1-Dimethylcyclopropane

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