The Question is from neet-chemistry coordination-compounds , and it was created by the author A.RAMA NAGESWARARAO

Question

An organic compound with molecular formula $C_6H_{10}$ exhibits optical isomerism and decolorizes bromine water. It does not show geometrical isomerism.  Which of the following could be the compound?

A.RAMA NAGESWARARAO · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Isomerism, Unsaturated Hydrocarbons, Optical Activity
 **Related Topics**:  Alkenes, Alkynes, Cycloalkenes, Stereoisomerism
 **Prerequisites**: Understanding of structural formulas, isomerism (structural, geometrical, optical), and reactions of alkenes and alkynes.
## SOLUTION PATHWAY
**Given Information**:
  Molecular formula: $C_6H_{10}$
  Exhibits optical isomerism
  Decolorizes bromine water (indicating unsaturation)
  Does not show geometrical isomerism
**Method & Steps**:
 1. Analyze the given information. The formula $C_6H_{10}$ suggests the compound is unsaturated (degree of unsaturation = 2).  The decolorization of bromine water confirms unsaturation (addition reaction across a double or triple bond).
  Reasoning: The presence of optical isomerism means the molecule is chiral (possesses a stereocenter).
  Formula/Rule: Degree of unsaturation = (2C + 2 + N - X - H)/2, where C is carbon, N is nitrogen, X is halogen, and H is hydrogen.
 2. Consider each option:
  Working: We need a chiral molecule with a double bond (or a ring) but without cis-trans isomerism.
  Key Point:  Optical isomerism requires a chiral center (a carbon atom with four different groups attached).
 3. Evaluate option C, 3-Methylcyclopentene:
  Result: 3-Methylcyclopentene has a double bond (explaining bromine water decolorization) and a chiral center (carbon atom bonded to methyl, hydrogen, and two different parts of the ring), fulfilling all conditions.
  Verification: It satisfies the molecular formula ($C_6H_{10}$), exhibits optical isomerism due to the chiral carbon, decolorizes bromine water (due to the double bond), and does not exhibit geometrical isomerism since the double bond is not part of a system capable of cis-trans isomerism.
## OPTION ANALYSIS
[A] Hex-3-yne :x: This is an alkyne with a triple bond, but it's not chiral and thus doesn't show optical isomerism.
[B] 2,3-Dimethylbuta-1,3-diene :x: This molecule is not chiral; it can exhibit geometrical isomerism.
[C] 3-Methylcyclopentene ✓: This molecule satisfies all given conditions: it has the correct molecular formula, decolorizes bromine water due to the double bond, is chiral and hence displays optical isomerism, and does not have geometrical isomerism.
[D] Cyclohexa-1,3-diene :x: This molecule is not chiral and can exhibit geometrical isomerism.
## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing geometrical and optical isomerism: Understanding the structural requirements for each type of isomerism is crucial.
  2.Ignoring the degree of unsaturation:  The formula $C_6H_{10}$ provides valuable information about the structure.
 **Quick Tips**:
  1.Draw the structures of each option to visualize their chirality and geometry.
  2.Memorize the structural features required for optical and geometrical isomerism.

A.RAMA NAGESWARARAO · Answer

Hex-3-yne

A.RAMA NAGESWARARAO · Answer

2,3-Dimethylbuta-1,3-diene

A.RAMA NAGESWARARAO · Answer

The correct Option is "3-Methylcyclopentene"

A.RAMA NAGESWARARAO · Answer

Cyclohexa-1,3-diene

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