Optical Isomerism Lecture Notes

Key Concepts

• Optical Isomerism: Shown by compounds with a chiral or asymmetric carbon.
• Chiral Carbon: A carbon atom bonded to four different atoms or groups.

Examples of Molecules with Chiral Carbons

1. Butan-2-ol
   • Contains a chiral carbon bonded to four different atoms or groups.
2. Lactic Acid
   • Also features a chiral carbon atom bonded to four distinct atoms or groups.

Characteristics of Optical Isomers (Enantiomers)

• 3D Configuration:
  • The four groups around the chiral carbon can be arranged in two three-dimensional configurations.
  • These configurations are mirror images of each other.
• Non-superimposable:
  • The mirror images cannot be superimposed onto each other, classifying them as enantiomers.

Drawing Optical Isomers

• Use a Stereochemical Formula to depict the spatial arrangement of atoms.
• Draw the two optical isomers as mirror images with a mirror in the middle.

Examples

• 3D models of butan-2-ol show non-superimposable mirror images.
• Lactic acid optical isomers are similarly drawn as mirror images using the stereochemical formula.

Optical Activity

• Optically Active: The optical isomers rotate plane-polarized light in opposite directions.

Note: Further details on optical activity with plane polarized light will be discussed in the next video.