Question

This compound forms a sodium salt upon reacting with $NaN{H}_2$. Identify the compound.

• A. $C_2{H}_2$
• B. $C_2{H}_4$
• C. $C_6{H}_6$
• D. $C_2{H}_6$

Answer 1

The correct option is A $C_2{H}_2$

Acetylene on reaction with $NaN{H}_2$, forms sodium salt.

$HC\equiv CH\stackrel{NaN{H}_2}{\to }\underset{sodiumacetylide}{HC\equiv C^{-}N{a}^{+}}\stackrel{NaN{H}_2}{\to }\underset{disodiumacetylide}{NaC\equiv CNa}$

The $sp$ hybridized carbon atom in acetylene has higher electronegativity as compared to $s{p}^2$ hybridized carbon atom in ethylene and $s{p}^3$ hybridized carbon atom in ethane. The carbon atom of $C-H$ bond in acetylene attracts the shared electron pair towards itself to a greater extent and the hydrogen atom can be easily liberated as the proton. Hence, the hydrogen atom attached to the triply bonded carbon atom in alkynes has appreciable acidic character.

When acetylene reacts with $NaN{H}_2$ which is the strong base reacts to form a sodium salt.