Tests For Alkenes And Alkanes

Question 1

What is the test for alkanes?

Answer 1

Alkanes react with chlorine and bromine in the presence of UV light forming haloalkanes.

This is known as a substitution reaction because the bromine replaces the hydrogen.

Question 2

What is the test for alkenes?

Answer 2

Halogens react with alkenes forming haloalkanes. For example bromine and ethene make dibromoethane.

These are addition reactions because the double bond splits and the halogen atom is added.

When you shake bromine water with an alkene it will go colourless but won’t with an alkane