CHM301 - CARBOXYLIC ACID DEPRIVATIVES

Chapter 4: Carboxylic Acid Derivatives

4.1 General Formula and Nomenclature

  • General Formula: RCO-Z (Z= nucleophilic substituent)

  • Nomenclature:

    • Acid Chlorides: Named by replacing "-ic acid" suffix with "-yl chloride".

    • Acid Anhydrides: Derived from two carboxylic acids.

    • Esters: Formed by replacing hydroxyl ( -OH) group with an alkoxy group ( -OR).

    • Amides: Created from carboxylic acid and ammonia or amine groups.

4.2 Nucleophilic Acyl Substitution Reactions

  • Mechanism involves:

    1. Nucleophile attacks the carbonyl carbon.

    2. Intermediate forms with a new bond.

    3. Leaving group departs.

4.3 Relative Reactivity of Nucleophilic Acyl Substitution

  • Reactivity ranks: Acid Chlorides > Anhydrides > Esters > Amides.

4.4 Preparation

4.4.1 Preparing Acid Chloride from Carboxylic Acids

  • Methods include the use of:

    • PCl5

    • SOCl2

    • PCl3

4.4.2 Preparing Acid Anhydrides from Dry Salts

  • Use acyl chlorides with carboxylate salts.

4.4.3 Preparing Esters from Carboxylic Acids and Acid Chlorides

  • Reaction with alcohols or phenols without catalyst.

4.4.4 Preparing Amides from Carboxylic Acids

  • Can also use ammonium carboxylates or acid chlorides.

4.5 Reactions

4.5.1 Hydrolysis Reactions

  • Hydrolysis of:

    • Acid Chlorides to form carboxylic acids and HCl fumes.

    • Acid Anhydrides yield two equivalents of the acid.

    • Esters yield carboxylic acid and alcohol.

    • Amides yield carboxylic acids in acidic or basic conditions.

4.5.2 Ammonolysis

  • Reaction of acid chlorides with ammonia or amines to form amides.

4.5.3 Alcoholysis

  • Acid chlorides and anhydrides react with alcohols to form esters.

4.5.4 Friedel-Crafts Acylation

  • Acyl chlorides and anhydrides react with aromatic compounds in the presence of AlCl3.

4.5.5 Transesterification

  • Exchange of alkyl groups in esters, can occur under acidic or basic conditions.

4.5.6 Reaction of Amides with Nitrous Acid

  • Converts amides to carboxylic acids and nitrogen gas (N2).

4.5.7 Reduction of Amides

  • Strong reducing agents like LiAlH4 reduce amides to amines.

4.5.8 Hofmann Degradation of Amides

  • Heating amides with Br2 and KOH converts them to amines.

4.5.9 Dehydration of Amides

  • Amides can be dehydrated to form nitriles using P2O5.

4.6 Chemical Tests for Carboxylic Acids and Derivatives

  • Distinguishing tests for:

    • Acid Chlorides: Produce white fumes in water.

    • Acid Anhydrides: Form carboxylic acid when hydrolyzed.

    • Esters: Hydrolyzed to produce carboxylic acid and alcohol.

    • Amides: Can yield ammonia upon hydrolysis.

Conclusion

  • Summary of carboxylic acid derivatives including structures, nomenclature, reactivity, preparation methods, reactions, and differentiating tests to distinguish between them.