1. $\mathop {C{H_3} - \mathop {\mathop {C{\mkern 1mu} {\mkern 1mu}  = {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} }\limits^{|{\kern 1pt} {\kern 1pt} {\kern 1pt} \,\,\,\,\,{\kern 1pt} {\kern 1pt} {\kern 1pt} } }\limits^{C{H_{3\,\,}}\,\,\,} C{H_2}}\limits_{{\text{Isobutene}}} $

2. $\mathop {C{H_3}C{H_2} - CH = C{H_2}}\limits_{{\text{1 - butene}}} $

3. $\mathop {\begin{array}{*{20}{c}}
  {{H_2}C{\mkern 1mu}  - C{H_2}} \\ 
  {|{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} \,\,\,\,\,\,{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} |} \\ 
  {{H_2}C - C{H_2}} 
\end{array}}\limits_{Cyclobu\tan e} {\mkern 1mu} $

4. $\underset{Trans-2-butene}{\mathop{\begin{matrix}
   ^{C{{H}_{3}}}  \\
   _{H}  \\
\end{matrix}\begin{matrix}
   \text{ }\!\!\backslash\!\!\text{ }  \\
   /  \\
\end{matrix}C=C\begin{matrix}
   /  \\
   \text{ }\!\!\backslash\!\!\text{ }  \\
\end{matrix}_{C{{H}_{3}}}^{H}}}\,$

5. $\underset{cis-2-butene}{\mathop{\begin{matrix}
   ^{C{{H}_{3}}}  \\
   _{H}  \\
\end{matrix}\begin{matrix}
   \text{ }\!\!\backslash\!\!\text{ }  \\
   /  \\
\end{matrix}C=C\begin{matrix}
   /  \\
   \text{ }\!\!\backslash\!\!\text{ }  \\
\end{matrix}_{C{{H}_{3}}}^{C{{H}_{3}}}}}\,$