$\text{Độ bất bão hòa:}\\
k = \dfrac{4.2+2-8}{2}=1\\
\Rightarrow \rm C_4H_8\ \text{có 1 liên kết $\pi$ hoặc 1 vòng}\\
\begin{array}{|c|c|}
\hline
\text{CTCT}&\text{Tên gọi}\\
\hline
\rm CH_2=CH-CH_2-CH_3&\rm But-1-en\\
\hline
\rm CH_3-CH=CH-CH_3&\rm cis-But-2-en\\
&\rm trans-But-2-en\\
\hline
\rm CH_2=\mathop{C}\limits_{\Big|}-CH_3&\rm 2-metylprop-1-en\\
\rm \quad CH_3&\rm (Isobutilen)\\
\hline
\rm H_2\mathop{C}\limits_{\Big|}-\mathop{C}\limits_{\Big|}H_2&\rm Xiclobutan\\
\rm H_2C-CH_2&\\
\hline
\rm \qquad \qquad \mathop{C}\limits_{\Big/ \ \ \ \Big\backslash}\kern-5ptH-CH_3&\rm Metylxiclopropan\\
\rm \ \ H_2C-CH_2&\\
\hline
\end{array}$
