Test for unsaturation

(i) By Br₂ in CCI₄ : The decolorization of 5% Br₂ in CCI₄ by a compound confirms the presence of unsaturation in molecule.

(ii) By Baeyers reagent : The decolorization of pink colour of 1% cold alkaline KMnO₄ by a compound confirms the presence of unsaturation in molecule.

Note :

(i) Alkenes without any hydrogen atom on olefinic bond do not show these tests e.g.

(ii) Aldehydes, primary and secondary alcohols which are readily oxidized by alk. KMnO₄ and thus decolorize alk. KMnO₄

To locate the position of unsaturation : By ozonolysis

To distinguish

(i) Alkane and alkene : By Br₂ in CCI₄ or By Baeyers reagent

(ii) Alkane and alkyne : As above

(iii) Alkene-1 and alkene-2 : By ozonolysis

(iv) Alkyne-1 and alkyne-2 : By Amm. AgNO₄ or Amm. Cu₂CI₂

To separation a mixture of alkane, alkene and alkyne-1

The mixture is passed through amm. Cu₂CI₂ or amm. AgNO₃ where alkyne-1 are retained in it and alkane, alkene mixture comes out. The mixture is then passed through conc. H₂SO₄ which absorbs alkene and alkane comes out.