Question

How is propyne prepared from an :
$\left(i\right)$ alkylene dihalide
$\left(ii\right)$ alkylidene dihalide and
$\left(iii\right)$ Tetrahaloalkane

Answer 1

(i) & (ii) Preparation of propyne from alkylene or alkylidene dihalide:-

$Br$ $Br$

$H_{3}C-\stackrel{|}{\underset{|}{C}}-\stackrel{|}{\underset{|}{C}}-H\underset{\left(2equi\right)}{\overset{NaN{H}_2}{\to }}\underset{\text{Propyne}}{C{H}_3-C\equiv CH}+2NaBr$

$H$ $H$

$\text{Propylene Dibromide}$

(iii) Preparation of propyne from Tetrahaloalkane:-

$Br$ $Br$

$H_{3}C-\stackrel{|}{\underset{|}{C}}-\stackrel{|}{\underset{|}{H}}\underset{Zn}{\overset{Heat}{\to }}\underset{Propyne}{H_{3}C-C\equiv C-H}+2ZnB{r}_2$

$Br$ $Br$