Introduction to Carbonyl Chemistry

Overview

• Introduction to carbonyl groups and their functional classes.
• Focus on Class 1 carbonyl groups, including esters, carboxylic acids, amides, and anhydrides.

Class 1 Carbonyl Groups

• Characteristics:
  • Good leaving groups.
  • Examples: Esters, carboxylic acids, amides, and anhydrides.

Reaction Mechanism

• Example with Anhydrides:
  • Nucleophile attacks carbonyl.
  • Double bond breaks, electrons donate back.
  • Oxygen acts as a leaving group.
  • Results in nucleophile added to carbonyl and release of oxygen.
• Class 1 vs Class 2 Carbonyls:
  • Class 2 (aldehydes, ketones) have poor leaving groups.
  • Class 1 has good leaving groups like acid chlorides.

Class 3 Carbonyls

• Focuses on alpha carbon and alpha hydrogens.
• Unique: Formation of enolates, different chemistry from Classes 1 and 2.

Reaction Mechanism for Class 1 Carbonyls

• Nucleophile attacks carbonyl carbon.
• Formation of tetrahedral transition state.
• Transition to new carbonyl species or revert to starting material.
• Equilibrium depends on nucleophile reactivity vs leaving group.

Examples of Class 1 Reactions

• Acid Chlorides:

  • With water or OH⁻: Forms carboxylic acids.
  • With alcohols: Forms esters.
  • With amines: Forms amides.
  • With carboxylic acids: Forms anhydrides.

• Carboxylic Acids:

  • With alcohols (under acidic conditions): Forms esters.
  • Cannot directly form amides due to amine protonation.
  • With another carboxylic acid (under acidic conditions): Forms anhydrides.

• Amides:

  • Requires heat to react due to stable form.
  • Can transform into carboxylic acids or esters with H⁺ and heat.
  • Cannot form anhydrides.

• Esters and Anhydrides:

  • Esters: Convert to carboxylic acids or other esters.
  • Anhydrides: Can form carboxylic acids, esters, and amides.

Conclusion

• Order of Reactivity:
  • Acid chlorides > Anhydrides > Carboxylic acids/Esters > Amides.
• Key Mechanisms:
  • Same mechanism repeated for class 1 carbonyls.
  • Watch video again and practice mechanisms.

Additional Notes

• Acid chlorides can only be formed from carboxylic acids using thionyl chloride.
• Importance of understanding leaving group ability and nucleophile reactivity.

Recommendation: Review mechanisms, practice regularly, and reach out for help if needed.