Lecture Notes: Stereochemistry and Chirality

Molecular Structures

• Molecule Representation
  • Carbon bonded to hydrogen (H), chlorine (Cl), bromine (Br), and fluorine (F).
  • Use of wedges and dashes to represent bonds:
    • Wedge: bond coming out towards the observer (e.g., bromine).
    • Dash: bond going away from the observer (e.g., fluorine).
  • Color Coding: Chlorine (yellow), Bromine (red), Fluorine (green).

Isomers

• Definitions
  • Isomers: Compounds with the same parts (atoms) but different arrangements.
  • Stereoisomers: Isomers differing in the 3D arrangement of atoms.
  • Structural/Constitutional Isomers: Not applicable here as the connectivity of atoms remains.

Stereochemistry

• Dot Structures
  • Example given with stereochemistry omitted to show base connections.
  • Highlighted how stereochemistry distinguishes stereoisomers.

Enantiomers

• Definition
  • Stereoisomers that are non-superimposable mirror images.
  • Example: Right molecule is a mirror image of the left but cannot be superimposed.

Chirality

• Chiral Center
  • Tetrahedral (SP3 hybridized) carbon bonded to four different atoms/groups.
  • Example: Carbon bonded to H, F, Br, Cl is a chiral center.
  • A chiral center leads to stereoisomerism.

Calculating Stereoisomers

• Formula: (2^n) where (n) is the number of chiral centers.
  • For one chiral center: (2^1 = 2) stereoisomers.
  • The stereoisomers discussed are enantiomers (non-superimposable mirror images).

Upcoming Topics

• Further exploration into chiral centers and identifying them in molecules.
• Detailed classification of stereoisomers.

Note

• Understanding stereochemistry and chirality is crucial for identifying molecule structures and their behaviors.