Degree of unsaturation is the no of H^₂ moleules required by the molecule 2 become saturated.

Ex: C₂H₄ : Ethene .

requires one molecule of H₂ to become saturated .so DU =1 .

 

Ex :

cyclopropane has the formula _^C3^H6.

IT REQUIRES 2 H TO become saturated. So. DU = 1 .

 

Cyclopropene has the fromula C₃H₄.

There is  double bond as wel as aring , so it needs 2 molecules of H₂ i.e. 4 H atoms , to become saturated.

 

Formula 4 DU = {( 2C + 2 ) + N + P - H -X } / 2

 

N - no of Nitrogen atom

P - no of phophorous toms.

H - no of H atoms .

X -no  of halogens.

C -no of carbons.