\(\begin{align} & C{{H}_{3}}\,-\,\,C{{H}_{2}}\,-\,C\equiv \overset{-}{\mathop{C}}\,\overset{+}{\mathop{N}}\,a\,\,\xrightarrow{C{{H}_{3}}\,-\,\,C{{H}_{2}}\,-\,\,C{{H}_{2}}\,-\,\,C{{H}_{2}}\,-\,\,Br} \\
& C{{H}_{3}}\,-\,\,C{{H}_{2}}\,-\,\underset{3\,\,-\,\,octyne}{\mathop{C{{H}_{2}}\,-\,\,C{{H}_{2}}\,-\,\,C}}\,\equiv C\,-\,\,C{{H}_{2}}\,\,-\,\,C{{H}_{3}} \\
\end{align}\)
$I. \,CH_3 - H$
$II.\, CH_3CH_2-H$
$III.\, CH_2 = CH - CH_2-H$
$IV.\, C_6H_5$