Preparation of carboxylic acid

• The preparation of carboxylic acids can be achieved through various methods, each involving specific reactants and conditions.

• Here is an overview of the primary preparation methods:

1. Oxidation of Primary Alcohols and Aldehydes

Oxidation of Primary Alcohols:

• Primary alcohols are oxidized to carboxylic acids using strong oxidizing agents such as potassium permanganate (KMnO4) or potassium dichromate (K2Cr2O7) under acidic conditions.

• Reaction: RCH2OH + 2[O] ⟶ RCOOH

• Example: Ethanol to Acetic Acid

• CH3CH2OH + 2[O]CH3​CH2​OH + 2[O] (from KMnO4) ⟶ CH3COOHCH3​COOH

Oxidation of Aldehydes:

• Aldehydes are converted to carboxylic acids using oxidizing agents like silver(I) oxide (Ag2O) or Tollens' reagent.

• Reaction: RCHO + [O] ⟶ RCOOH

• Example: Acetaldehyde to Acetic Acid

  • CH3CHO + [O]CH3​CHO + [O] (from Ag2O) ⟶ CH3COOHCH3​COOH

2. Oxidation of Alkyl Side Chains of Aromatic Compounds

• Alkylbenzenes with a benzylic hydrogen can be oxidized to aromatic carboxylic acids using oxidizing agents like potassium permanganate (KMnO4) or chromium trioxide (CrO3) in acidic medium.

• Reaction: Ar-CH3 + 2[O] ⟶ Ar-COOH

• Example: Toluene to Benzoic Acid

  • C6H5CH3+2[O]C6​H5​CH3​+2[O] (from KMnO4) ⟶ C6H5COOHC6​H5​COOH

3. Hydrolysis of Nitriles

• Nitriles can be hydrolyzed into carboxylic acids under either acidic or basic conditions, producing ammonia as a byproduct.

• Reaction: RC≡N + 2H2O ⟶ RCOOH + NH3

• Example: Acetonitrile to Acetic Acid

  • CH3C≡N + 2H2OCH3​C≡N + 2H2​O ⟶ CH3COOH + NH3CH3​COOH + NH3​

4. Carboxylation of Grignard Reagents

• Grignard reagents react with carbon dioxide to form carboxylate salts, which can be subsequently acidified to yield carboxylic acids.

• Reaction: RMgX + CO2 ⟶ RCOOMgX followed by RCOOMgX + H3O+ ⟶ RCOOH + MgX(OH)

• Example: Methyl magnesium bromide to Acetic Acid

  • CH3MgBr+CO2CH3​MgBr+CO2​ ⟶ CH3COOMgBrCH3​COOMgBr

  • Then, CH3COOMgBr + H3O + CH3​COOMgBr + H3​O+ ⟶ CH3COOH + MgBr(OH)CH3​COOH + MgBr(OH)