Question

Chemical test of saturated and unsaturated hydrocarbons

Answer 1

Bromine-water test:  Br2water is a brown coloured liquid.
(a) Unsaturated hydrocarbons give addition reaction with Br2. So the colour of Br2-water gets decolourized.
            R-C=C-R + Br2 →R-BrC-CBr-R

(b) Saturated hydrocarbons do not react with Br2-water, so the colour of Br2.-water does not get decolourised .

HOPE IT HELPS YOU

Answer 2

___________________________________________________

By adding  cold dilute Baeyer's reagnant

More about Baeyer's Reagnant.

• Baeyer's reagnant is cold dilute

• It is an oxidising agent.

If this mixture is added to an unsaturated compounds such as alkenes or alkanes then :

• Purple colour of  changes .

• It is first converted to a green compound   which is unstable in alkaline medium.

• This again changes to brown  

• The supernatant liquid gets decolourised.

However saturated compounds do not respond to the above test.

In simple words........... your answer is :

In order to test unsaturation first add cold dilute Baeyer's reagnant.

If the reagnant decolorises from purple to colourless then the compound is unsaturated

Otherwise if the reaction does not occur , then it is a saturated compound.

__________________________________________