CIE AS Chemistry (9701) exams from 2022

Revision Notes

3.5.5 Iodoform Reaction

Iodoform Reaction

  • Tri-iodomethane (also called iodoform) forms a yellow precipitate with methyl ketones
    • Methyl ketones are compounds that have a CH3CO-group
    • Ethanal also contains a CH3CO- group and therefore also forms a yellow precipitate with iodoform
  • The reagent is heated with an alkaline solution of iodine
  • This reaction involves a halogenation and hydrolysis step
    • In the halogenation step, all three H-atoms in the -CH3 (methyl) group are replaced with iodine atoms, forming a -CI3 group
    • The intermediate compound is hydrolysed by an alkaline solution to form a sodium salt (RCO2 Na+) and a yellow precipitate of CHI3

Carbonyl Compounds Iodoform Test, downloadable AS & A Level Chemistry revision notes

The reaction of ethanal with iodoform results in the formation of a yellow CHI3 precipitate

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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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