Determination of fat unsaturation

Determination of oil unsaturation using bromine water

Scientific name: Qualitative reaction for double bonds is the reaction of unsaturated compounds with bromine water.


Testing for unsaturation in oils - Bromine added to oils

by Scott Milam

Определение непредельноси жиров

by ФизматФильм


Use protective googles and gloves. Be careful with bromine water. Use ground-in-tube stopper.

Always follow general safety recommendations. Please note that conducting chemistry experiments you must comply with the relevant legal procedures in your country.

Reaction formula

-CH2-CH=CH-CH2- + Br2 → -CH2-CHBr-CHBr-CH2-


  1. Bromine water

Step-by-step instruction

  1. Take a test-tube and pour 5 ml of oil into it. You can use sunflower or olive oil.
  2. Use protective googles and gloves. Carefully add 3 ml of bromine water into the test-tube.
  3. Close the tube using the stopper and shake the tube. The bromine water becomes discolored.

Scientific background

Vegetable oils are triglycerides extracted from a plant. Triglycerides are an ester derived from glycerol and three fatty acids. Fatty-acid-residues can be saturated and unsaturated compounds. Unsaturated compounds have double bonds (C=C) between carbon atoms. Unsaturated fats have a lower melting point and are more likely to be liquid at room temperature. Vegetable oils are more unsaturated then animal fats.

The double bonds have the ability to attach halogen atoms. The qualitative reaction for double bonds is the reaction of unsaturated compounds with bromine water:

-CH2-CH=CH-CH2- + Br2 → -CH2-CHBr-CHBr-CH2-

Discoloration of bromine water is the qualitative indication of this reaction.


Published on 11 October 2015

  • Fire
  • Heating with fire
  • Explosion
  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst