# How "degrees of unsaturation" are associated with a C_8H_10 formula?

Mar 16, 2017

Well the formula ${C}_{8} {H}_{10}$ has 4 degrees of unsaturation ......

#### Explanation:

The saturated formula would be ${C}_{8} {H}_{18}$, and thus the given formula ${C}_{8} {H}_{10}$ has $\text{4 degrees of unsaturation}$.

And each degree of unsaturation CORRESPONDS to an olefinic bond, i.e. $C = C$ OR a RING JUNCTION.

And thus the pictured $\text{xylene}$, as well as any one of its other 2 isomers (which are?) could correspond to the formula. And by my count $\text{xylene}$ has $8 \times C - C$ $\sigma$ bonds, $10 \times C - H$ $\sigma$ bonds, and, formally, $3 \times C - C$ $\pi$ bonds.........

By joining and fusing rings, we could form a structure where the distinction between $\sigma$ and $\pi$ bonds are less ambiguous, however, these would be less common structures than the benzene derivative.

Note that the $\text{degree of unsaturation}$ is a very useful criterion with which to assess organic molecules.