CIE A Level Chemistry (9701) exams from 2022

Revision Notes

7.5.1 Production of Benzoic Acid

Production of Benzoic Acid

  • Benzoic acids are the simplest aromatic carboxylic acids with the molecular formula of C6H5COOH
  • Benzoic acids and their derivatives are often used as reagents in the synthesis of esters
  • The compounds can be produced from the oxidation of alkylbenzenes

Oxidation of alkylbenzenes

  • The alkyl side-chain in alkylbenzenes, such as methylbenzene, can be oxidised to a carboxylic acid
  • The alkylbenzene is heated under reflux with a solution of hot alkaline KMnO4 (this is the oxidising agent)
    • The purple colour of the Mn7+ ions disappears as they are reduced to Mn4+ ions
    • A brown precipitate of MnO2 is formed
  • The mixture is then acidified with dilute acid (such as hydrochloric acid) to protonate the organic product form and produce a benzoic acid

Carboxylic Acids _ Derivatives - Production of benzoic acid, downloadable AS & A Level Chemistry revision notes

Alkylbenzenes such as methylbenzene undergo oxidation to form benzoic acid

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Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.

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