c
$C{{H}_{3}}-C{{H}_{2}}-C\equiv CH+HCl\to $ $\begin{matrix}
C{{H}_{3}}C{{H}_{2}}-C=C{{H}_{2}} \\
\,\,\,\,\,\,\,\,\,\,\,| \\
\,\,\,\,\,\,\,\,\,\,\,\,Cl \\
\end{matrix}\xrightarrow{HI}$ $\underset{2-chloro-2-iodo\,bu\tan e}{\mathop{\begin{matrix}
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,I \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,| \\
C{{H}_{3}}-C{{H}_{2}}-C-C{{H}_{3}} \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,| \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,Cl \\
\end{matrix}}}\,$