Edexcel A Level Chemistry:复习笔记7.3.2 Preparation of Carboxylic Acids

Preparation of Carboxylic Acids


  • Carboxylic acids are compounds with a -COOH functional group
  • They can be prepared by a series of different reactions

Oxidation of primary alcohols & aldehydes

  • Carboxylic acids can be formed from the oxidation of primary alcohols and aldehydes by either acidified K2Cr2O7 or acidified KMnO4 and reflux
  • The oxidising agents themselves get reduced causing the solutions to change colour
    • In K2Cr2O7 the orange dichromate ions (Cr2O72-) are reduced to green Cr3+ ions
    • In KMnO4  the purple manganate ions (MnO4-) are reduced to colourless Mn2+ ions



Oxidation of primary alcohols (1) and aldehydes (2) gives carboxylic acids


Hydrolysis of nitriles

  • Carboxylic acids can also be prepared from the hydrolysis of nitriles using either dilute acid or dilute alkali followed by acidification
    • Hydrolysis by dilute acid results in the formation of a carboxylic acid and ammonium salt
    • Hydrolysis by dilute alkali results in the formation of a sodium carboxylate salt and ammonia; Acidification is required to change the carboxylate ion into a carboxylic acid


  • The -CN group at the end of the hydrocarbon chain is converted to a -COOH group


Hydrolysis of nitriles by either dilute acid (1) or dilute alkali and acidification (2) will form a carboxylic acid