Question: Determine the degree of unsaturation and then draw possible structures for noncyclic compounds with the following molecular formulas:

a. C₃H₆

b. C₃H₄

c. C₄H₆

The degree of unsaturation (sometimes referred to as the index of hydrogen deficiency (IHD), double bond equivalents, or unsaturation index) is a computation that determines the total number of rings and bonds in a compound.

The degree of unsaturation of a chemical is defined as the total number of p bonds and rings.
The tetravalency of carbon is used to calculate the degree of unsaturation of an organic molecule.

C₃H₆ =Degree of Unsaturation = 1

C₃H₄= Degree of Unsaturation= 2

C₄H₆ =Degree of Unsaturation=2

• Because the alkene's double bond causes it to contain two less hydrogens than an alkane with the same number of carbons, the usual molecular formula for an acyclic alkene is also C_nH_2n.
• A cyclic alkene's general molecular formula must be C_nH_{2n - 2.}