Practicals test 2

Question 1

Describe the principle of one of the methods used during practicals to detect the presence of double bonds in unsaturated fatty acids.

Answer 1

Addition of Halogens: Chlorine, Fluorine, Bromine, Iodine, Astatine
The double bond of unsaturated fatty acids becomes saturated through addition of Halogen’s atoms to the neighbouring carbon atoms.
In the presence of Bromine water fatty acids become insoluble and a disappearance of yellow colour of bromine water can be observed in this reaction.
Add chloroform and oil to a test tube
Next add bromine water
Mix well and observe the change of colour. The yellow colour of bromine will disappear and the chloroform phase becomes cloudy doe to precipitation of insoluble fatty acids