Question

Give the method of preparation of ethyne by 1, 2-dibromoethene.

Answer 1

When 1, 2-dibromoethane (ethylene dibromide) is boiled with alcoholic potassium hydroxide, ethyne is formed.

\[\begin{array}{cc}
\ce{CH2Br + \underset{(alcoholic)}{2KOH} ->[200^\circ C][boiling] CH + 2KBr + 2H2O}\\
|\phantom{.......................}|||\phantom{...................}\\
\phantom{...}\ce{CH2Br}\phantom{................}\ce{\underset{(Ethyne)}{CH}}\phantom{...................}
\end{array}\]