Carboxylic Acids

Introduction to Carboxylic Acids

Carboxylic acids are weak acids which are only partially ionised in aqueous solution. They are characterised by the carboxyl functional group (COOH). Carboxylic acids can often be recognised by their distinctively unpleasant smells. To test for a carboxylic acid, a colourless gas is evolved (CO₂) on the addition of sodium carbonate.

Preparation of Carboxylic Acids

Carboxylic acids can be prepared by

• Oxidation of an aldehyde.
• Nucleophilic addition-elimination of an acid chloride

Reactions of Carboxylic Acids

• Esterification

  Carboxylic acids react with alcohols to form esters in an acid catalysed reaction. (This reaction is reversible, the reverse hydrolysis reaction is shown under esters). An example mechanism is shown below for a carboxylic acid ROOH reacting with an alcohol R'OH under acidic conditions, (where R and R' are alkyl groups).

  The reaction can be driven forward by Le Chatelier's principle by using excess acid (or alcohol) or removing water.
  

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