Degree of Unsaturation ( D.U.)

Degree of Unsaturation ( D.U.) or Index of Hydrogen deficiency (I.H.D)

Degree of Unsaturation ( D.U.) is defined as total sum of total pi π bonds and no. of cycles (rings) in a compound.

DU from Structural formula.

Example 1. Cyclobutadiene. Cyclobutadiene has two pi bonds and one ring hence the D.U. of Cyclobutadiene is 2+1 = 3.

Example 2. Napthalene Napthalene has 5 pi bonds and two ring hence the D.U. of Napthalene is 5+2 = 7.

Example 3. Pthallic acid Pthallic Acid has 5 pi bonds and one ring hence the D.U. of Pthallic Acid is 5+1 = 6.

Example 4. Bombykol Bombykol has 2 pi bonds and no ring hence the D.U. of Bombykol is 2+0 =2.

Example 4. Benzonitrile Benzonitrile has 5 pi bonds and one ring hence the D.U. of Benzonitrile is 5+1 =6.

Example 5. Cubane Cubane has no pi bonds and five ring hence the D.U. of cubane is 0+5 =6.

DU from Molecular Formula.

If molecular formula of a compound is

C _nH _mCl _xO _yN _z

then D.U. is


Example 1 For

C ₁₀H ₂₀

n =10 and m= 20 x =0 y =0 Z=0 hence D.U. = 1.

Example 2 For

C ₁₀H ₈

n =10 and m= 8 x =0 y =0 Z=0 hence D.U. = 14/2 =7.

Example 3 For

C ₁₀H ₈Cl ₂

n =10 and m= 8 x =2 y =0 Z=0 hence D.U. = (22-8-2)/2 =6.