What are the isomers of C_4H_8?

1 Answer
Aug 14, 2016

I count 5 structural isomers............

Explanation:

One of the structural isomers has a geometric isomer.

$\text{1. cyclobutane}$; $\text{2. methylcyclopropane}$; $\text{3. 1-butylene}$; $\text{4. 2-butylene}$; $\text{5. 2-methylpropene}$.

$\text{2-butylene}$ can of course generate 2 geometric isomers, which are?

Just to add a bit more method to the analysis. It is a fact that an alkane has general formula ${C}_{n} {H}_{2 n + 2}$. In this analysis, an halide counts for $H$, oxygens are ignored (they can be carbonyls or alcohols or ethers), and if there is a $N$ in the compound, we subtract $N H$ from the given formula. Each 2 hydrogens less than this formula corresponds to a degree of unsaturation. A degree of unsaturation corresponds to an olefinic bond, OR a ring junction. Thus I knew that the possible isomers of ${C}_{4} {H}_{8}$ were olefins, OR $\text{3- or 4-membered rings}$.