Understanding Stereoisomers and Chirality

Oct 23, 2024

Lecture on Stereisomers

Introduction to Isomerism

  • Isomerism: Concept where molecules have the same molecular formula but different structures or orientations.
  • Structural Isomers: Molecules with the same molecular formula but different connectivity.
    • Example: Straight-chain butane vs. isobutane (C4H10).

Stereoisomers

  • Definition: Compounds with the same molecular formula and connectivity, differing in 3D orientation.
  • Types:
    • Enantiomers
    • Diastereomers

Enantiomers

  • Definition: Molecules that are non-superposable mirror images.
    • Analogous to left and right hands as non-superposable mirror images.
  • Example: A molecule reflected across a mirror plane may not overlap properly with the original.

Characteristics of Enantiomers

  • Chirality: Quality of having non-superposable mirror image.
    • Chiral Center: A carbon with four different substituents.
    • Example:
      • A carbon with bromine, hydrogen, and two different carbon chains is chiral.
      • A carbon with bromine, hydrogen, and two identical methyl groups is not chiral.
  • Achiral Molecules: Molecules with superposable mirror images.
    • Example:
      • A molecule with two identical fluorine atoms.
      • Achiral due to identical substituents or ability to superpose mirror images.

Conclusions

  • Chiral vs. Achiral: Understanding stereoisomerism helps identify if a molecule has a non-superposable mirror image (chiral) or a superposable one (achiral).

Additional Information

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