How do you detect the presence of double bond in a molecule?
Answers
Explanation:
Presence of double bond in an organic compoud represents that it is unsaturated in nature ,therefore unsaturation tests are used to confirm presence of double bond in any compound.
Unsaturation tests :-
1.Potassium permanganate test or Baeyer’s reagent test :-
*In this test given organic compound is treated with alkaline solution of potassium permanganate (KMnO4) which is purplish-pink in color.
*If this colour is faded to brown from purplish pink by adding the unknown compound then it confirms the presence of unsaturated compound either it be double bonded or triple bonded.
2.Bromine test :-
* When an organic compound treated with small amount of elemental bromine (Br2) in an organic solvent like CCl4 and proceeds the reaction then disappearance of deep brown colour of bromine is observed.This disappearance ends with white precipitate or transparent solution.
* Higher the unsaturation more will be the transparency.
* Hence we can confirm the presence of double or triple bond in an org compound.
But in case of alkene ,there may be the chance that brown colour of bromine doesn't disappear because alkenes reacts very slowly with Bromine and our test doesn't make confirmation. Thatswhy we prefer Baeyer ‘s reagent test for alkene or other double bonded compounds over Bromine test.