Question

State the conditions required for the Preparation of ethyne from ethylene dibromide

Answer 1

• Acetylene ($C_2{H}_2$) is the first member of the alkyne series. $IUPAC$ name of Acetylene is Ethyne. Alkynes are hydrocarbons with Carbon-Carbon triple bond ($C\equiv C$).
• They have the root word with suffix ‘-yne’. It comes with the general formula $C_n{H}_{2n-2}$.
• Ethyne is made by reacting Ethylene dibromide ($C_2{H}_{4}B{r}_2$) with hot conc. alcoholic $KOH$.
• The chemical reaction is as follows.

$$\begin{gathered} \underset{\underset{\mathrm{dibromide}}{\mathrm{Ethylene}}}{{\mathrm{C}}_2{\mathrm{H}}_4{\mathrm{Br}}_2}\left(g\right)+\underset{\underset{\mathrm{hydroxide}}{\mathrm{Potassium}}}{\mathrm{KOH}\left(\mathrm{alcoholic}\right)}\to \underset{\underset{\mathrm{bromide}}{\mathrm{Vinyl}}}{\mathrm{CHBr}={\mathrm{CH}}_2\left(\mathrm{g}\right)}+\underset{\underset{\mathrm{bromide}}{\mathrm{Potassium}}}{\mathrm{KBr}\left(\mathrm{s}\right)} \\ \underset{\underset{\mathrm{bromide}}{\mathrm{Vinyl}}}{\mathrm{CHBr}={\mathrm{CH}}_2}\left(\mathrm{g}\right)+\underset{\underset{\mathrm{amide}}{\mathrm{Sodium}}}{{\mathrm{NaNH}}_2}\left(\mathrm{s}\right)\to \underset{\mathrm{Ethyne}}{\mathrm{CH}\equiv \mathrm{CH}}\left(\mathrm{g}\right)+\underset{\underset{\mathrm{bromide}}{\mathrm{Sodium}}}{\mathrm{NaBr}}\left(\mathrm{s}\right)+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)} \end{gathered}$$