# How many structural isomers can be proposed for a formula of C_4H_8?

Feb 4, 2017

${C}_{4} {H}_{8}$ has one degree of unsaturation, and thus whatever the compound we have the one degree of unsaturation, i.e. one olefinic bond, or 1 ring junction.
So I count 2 ring structures: $\text{cyclobutane}$; and $\text{methylcyclopropane.}$
And I count 3 olefinic structural isomers: $\text{1-butylene}$; $\text{2-butylene}$; $\text{2-methylpropene}$. $\text{2-butylene}$ can exist as 2 geometric isomers, which are?