3.4.4 Test for Unsaturation

Question 1

How can we test for unsaturation?

Answer 1

• Add bromine water
• Shake
• Orange to colourless if positive

Question 2

What is the chemistry behind the bromine water test for unsaturation?

Answer 2

• Br2 is orange in colour
• When added to sample of unsaturated compound
• Electrophilic addition occurs across the C=C bond
• Say C2H4 (ethene) was the alkene
• C2H4Br2 would form, which is colourless, so the Br2 molecule is no longer in solution, hence the sample turns from orange to colourless