CHEMISTRY – Tests for Presence of Organic Compounds

In Organic Chemistry, students will ‘encounter’ questions on the test of unsaturated organic compounds (typically alkene) and alcohol, which is less common.

Firstly, unsaturated organic compound is defined as an organic compound with double or triple carbon-carbon bond. As unsaturated organic compound react with bromine, bromoalkane, in an addition reaction with bromine, known as bromination.

For the identification of alcohol, students need to recognise that alcohol can oxidise to carboxylic acid, specifically with the use of an oxidising agent, solution of acidified potassium manganate(VII). During this process, the solution of acidified potassium manganate(VII) will turn from purple to colourless.

Hence, in summary,

  1. An unsaturated organic compound can be tested by adding aqueous bromine into the compound. Bromine will turn from brown to colourless.
  2. Alcohol can be tested by adding solution of acidified potassium manganate(VII) solution, under reflux. The solution of acidified potassium manganate(VII) will turn from purple to colourless.
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