Question

A hydrocarbon reacts with ammonical cuprous chloride solution to form a red precipitate, thehydrocarbon is –
(a) Ethane
(b) ethane
(c) butane
(d) 1-propyne

Answer 1

(d) 1-propyne hydrocarbon reacts with ammonical cuprous chloride solution to form a red precipitate

Answer 2

A hydrocarbon reacts with ammonical cuprous chloride solution to form a red precipitate, the hydrocarbon is (d) 1-propyne.

The chemical reaction involved in this process is given below:

$\mathrm{CH}_{3}-\mathrm{C}=\mathrm{CH}+\mathrm{CuCl}+\mathrm{NH}_{3} \rightarrow \mathrm{CH}_{3}-\mathrm{C}=\mathrm{C}-\mathrm{Cu}+2 \mathrm{NH}_{4} \mathrm{Cl}$

It is a typical identification test for alkyne. The chemical formula of 1-propyne is $\mathrm{CH}_{3}-\mathrm{C}=\mathrm{CH}$

Here, the triple bonded C atoms has one H atom. This H atom which is bonded with triple bonded C atom is called as acidic hydrogen atom. It can easily replace with $\mathrm{Cu}^{+2} \text { or } \mathrm{Ag}^{+}$ ions that will give precipitate of copper or silver ion.