Question

Sodium does not normally react with

• A. Ammonia Gas
• B. But-2-yne
• C. Ethyne
• D. Propyne

Answer 1

The correct option is B

But-2-yne

The correct answer is option B.

Explanation of correct answer:-

• The compound should have acidic hydrogen in order to react with sodium metal.
• Since, But-2-yne lacks terminal acidic hydrogen so it does not react with Na(sodium metal).
• In But-2-yne, both the carbons involved in triple bonding do not have a hydrogen atom and the terminal carbon atoms are $\text{'}{\mathrm{sp}}^3\text{'}$ hybridized that means it has less ‘s’ character in them, therefore the tendency to donate H+ ion will be less.
• Hence but-2-yne has 0 acidic hydrogen and does not react with sodium metal.

Explanation of incorrect answers:-

Option A

• Ammonia gas reacts with Na(sodium metal) to form sodamide $\left({\mathrm{NaNH}}_2\right)$ with the release of hydrogen gas.
• Sodium ionises in liquid ammonia, producing a Na⁺ ion and an electron. Ammonia is used to dissolve the electron.

Option C

• Ethyne is an alkyne that has acidic terminal hydrogen required to react with sodium metal (Na).
• Ethyne reacts with sodium metal and sodamide to form sodium acetylide with the liberation of dihydrogen gas.

Option D

• Propyne has acidic terminal hydrogen.
• The reduction of propyne with sodium in liquid ammonia gives prop-1-ene.

Therefore, option (B) is the correct answer.