Lecture 12-2: Multi-step Synthesis

Introduction to Multi-step Synthesis

• Focus on moving from starting compounds to target compounds through a series of reactions.
• Unlike single-step reactions, multi-step synthesis requires a sequence of reactions.

General Strategy

• Write reactions left to right in a flowchart format.
• Example:
  • Stockroom: Compound A, Reagent B, Reagent D.
  • Target Compound: E.
  • Steps:
    1. React A with B to form C.
    2. React C with D to form E.
• Multi-step synthesis involves creative and logical problem-solving.

Important Notes

• Do not balance reactions in multi-step synthesis.
• Reagents are not catalysts and are written above reaction arrows.
• Refer back to knowledge of mechanisms and reactions.

Example 1: Alcohol to Bromine-Cyanide Compound

• Stockroom: Alcohol, Sulfuric Acid, Br₂, Sodium Cyanide.
• Target Molecule: Compound with a bromine and cyanide group.
• Steps:
  1. Dehydration Reaction: Convert alcohol to alkene using sulfuric acid.
  2. Electrophilic Addition: Use Br₂ and cyanide to add Br and CN across the double bond.

Example 2: Alkene to Ketone

• Stockroom: Alkene, Sulfuric Acid, Water, Chromic Acid.
• Target Molecule: Ketone.
• Steps:
  1. Electrophilic Addition of Water: Convert alkene to secondary alcohol using water and acid.
  2. Oxidation: Convert secondary alcohol to ketone using chromic acid.

Conclusion

• Multi-step synthesis problems require practice and understanding of reactions.
• Further examples will be worked through in class worksheets.