$\begin{array}{*{20}{c}}
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,OH} \\
{\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,} \\
{C{H_3} - CH = CH - C{H_2} - CH - C{H_3}}
\end{array}$ $\longrightarrow $ $C{H_3} - CH = CH - C{H_2}C{O_2}H$
${C_2}{H_5}O\,{C_2}{H_5}\, + \,4[H]\,\xrightarrow{{HI}}\,2X\, + \,{H_2}O$
આ પ્રક્રિયામાં $X$ શું છે ?