Overview of Grignard Synthesis Techniques

Feb 13, 2025

Lecture 12-4: Grignard Synthesis

This lecture covers the specifics of performing a Grignard synthesis, focusing on the final recording for Chapter 12. The lecture is more of an overview, with detailed examples to be covered in class worksheets.

Grignard Synthesis Guidelines

  • Target Molecule: Identify the required molecule and available starting materials in the stockroom.
  • Carbon-Carbon Bond Formation: Focus on the alcohol group as the site for the new bond.
  • Alcohol Type Identification:
    • Primary, secondary, or tertiary alcohol will guide the selection of the oxygen-containing compound (aldehyde, ketone, ester, or epoxide).

Stockroom Considerations

  • Ensure availability of alkyl halides and oxygen-containing compounds.
  • Conversion might be necessary if certain materials are unavailable.
  • Grignard reactions involve three main steps.

Example 1: Ketone to Tertiary Alcohol

  • Process:
    • Identify the carbon-carbons to bond using dots.
    • Draw a line between them to indicate new bond.
    • Ketones always produce tertiary alcohols.

Example 2: Aldehyde to Secondary Alcohol

  • Strategy:
    • Use dots to identify reactive carbons.
    • Attach functional groups accordingly.
    • Aldehydes result in secondary alcohols.

Example 3: Ester to Tertiary Alcohol

  • Important Notes:
    • Requires two Grignard reagents.
    • Two covalent bonds form, requiring strategic placement of dots.
    • Esters always result in a tertiary alcohol.

Example 4: Epoxide Versatility

  • Versatility: Convert to primary, secondary, or tertiary alcohol.
  • Mechanism:
    • Grignard reagent adds to the least substituted carbon.
    • The location of the oxygen atom is critical in determining the structure of the product.
  • Product Types:
    • Two hydrogen R groups yield primary alcohol.
    • One alkyl and one hydrogen yield secondary alcohol.
    • Two alkyl groups yield tertiary alcohol.

Class Activities

  • Further exploration of multi-step synthesis problems.
  • Reverse engineering problems from target molecules.

Conclusion

  • The lecture covers the end of Chapter 12, with practical applications and problem-solving exercises to follow in class.