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Understanding Isomerism in Chemistry

May 6, 2025

Chemistry Lecture: Isomerism

Introduction

  • Lecture is part of B Tech Applied Science, Unit 5 Chemistry.
  • Topic: Isomers
    • Focus on structural and stereoisomerism.
  • Recommended to review previous videos on different types of formulas (displayed, structural, skeletal).
  • Objective: Recall and identify different types of isomerism.

Overview of Isomerism

  • Isomerism: Compounds with the same molecular formula but different arrangements of atoms.
  • Two main types:
    1. Structural Isomerism
    2. Stereoisomerism

Structural Isomerism

  • Definition: Same molecular formula, different structural formula.
  • Subgroups of Structural Isomerism:
    1. Chain Isomerism
      • Variation in arrangement of carbon atoms.
      • Examples: Straight chain vs. branched (e.g., C₅H₁₂ - pentane, 2-methylbutane, dimethylpropane).
    2. Position Isomerism
      • Difference in position of functional groups.
      • Example: Alkenes (But-1-ene vs. But-2-ene), Haloalkanes (2-bromobutane vs. 1-bromobutane).
    3. Functional Group Isomerism
      • Same molecular formula, different functional groups.
      • Examples: Cyclic alkanes vs. alkenes (Cyclohexane vs. Hexene), Aldehydes vs. Ketones (Propanal vs. Propanone).

Stereoisomerism

  • Definition: Same structural formula but different 3D arrangement in space.
  • Types of Stereoisomerism:
    1. Geometric Isomerism (EZ Isomerism)
      • Occurs in alkenes due to restricted rotation around the double bond.
      • Example: Arrangement of CH₃ groups in alkenes.
      • Important to use rules for assigning priority in naming.
    2. Optical Isomerism
      • Non-superimposable mirror images (chiral or asymmetric carbons).
      • Chiral carbon has four different groups attached (e.g., CH₃, H, OH, Cl).
      • More advanced topic, often covered at A-level rather than B Tech.

Conclusion

  • Review of different types of isomers.
  • Geometric isomerism is emphasized for further study.
  • Optical isomerism should be recognized but not deeply studied in B Tech.
  • Encouraged to watch detailed videos on geometric isomerism for deeper understanding.

Full transcript