Carboxylic acids can be prepared in the laboratory by several methods. Here are the main laboratory preparations explained in simple terms:
1. Oxidation of Primary Alcohols
- Primary alcohols, when oxidized with strong oxidizing agents like acidified potassium permanganate or potassium dichromate, give carboxylic acids.
- Example: ethanol gives ethanoic acid.
2. Oxidation of Aldehydes
- Aldehydes are easily oxidized to carboxylic acids using mild oxidizing agents such as Tollens’ reagent or Fehling’s solution.
- Example: ethanal gives ethanoic acid.
3. Hydrolysis of Nitriles
- Nitriles (–CN group) on hydrolysis with acids or bases yield carboxylic acids.
- Example: ethanenitrile gives ethanoic acid.
4. Hydrolysis of Esters
- Esters react with dilute acids or alkalis to give carboxylic acids and alcohols.
- Example: ethyl ethanoate gives ethanoic acid and ethanol.
5. Carbonation of Grignard Reagents
- A Grignard reagent (RMgX) reacts with carbon dioxide, and after hydrolysis, forms a carboxylic acid.
- Example: methyl magnesium bromide with CO₂ gives acetic acid.