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Understanding Isomers and Their Types

Feb 13, 2025

Lecture on Isomers

Definition of Isomers

  • Isomers are molecules with the same molecular formula but different structural formulas.
  • Molecular formula: The actual number of atoms in a molecule.
  • Structural formula: The arrangement of atoms in a molecule.

Examples of Isomers

  1. Aldehydes vs. Ketones

    • Both have the molecular formula CnH2nO.
    • Ketone: Carbon double-bonded to oxygen is in the middle.
    • Aldehyde: Carbon double-bonded to oxygen is at the end.

  2. Esters vs. Carboxylic Acids

    • Example molecular formula: C3H6O2
    • Carboxylic Acid: Contains the COOH group.
    • Ester: Contains a random oxygen in the chain.

  3. Alcohols

    • Both have the molecular formula C4H9OH.
    • Difference by the position of the OH group:
      • Middle of the chain vs end of the chain.

  4. Alkanes

    • Example with four carbons:
      • Different structures due to chain configuration.
      • Continuous chain of 4 carbons vs. branched structure.

Types of Isomerism

  1. Functional Isomerism

    • Different functional groups (e.g., ketone vs. aldehyde).

  2. Positional Isomerism

    • Same functional group in different positions on the carbon chain.
    • Example: Alcohols with OH group in different positions.

  3. Chain Isomerism

    • Different carbon chain arrangements.
    • Same molecular formula but different branching.

Key Takeaways

  • Isomers have the same molecular formula but different structural formulas.
  • Three types of isomerism: Functional, Positional, and Chain.
  • Chain isomerism involves different backbone structures while maintaining the same number of total carbons.

Conclusion: Understanding isomers involves recognizing that molecules can share molecular formulas but differ in structural orientation, leading to different physical and chemical properties. Further exploration of branches and structures will be covered in future lessons.

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