Question

Which of the following gases is evolved as a byproduct (A) in the following reaction,
\(\text{HC}\equiv \text{CH}+\text{LiNH}_{2}\xrightarrow{\text{solvent}}\text{HC}\equiv \text{C}^{-}\text{Li}^{+}+(\text{A})\)

• A. \(\text{N}_{2}\)
• B. \(\text{H}_{2}\)
• C. \(\text{NH}_{3}\)
• D. \(\text{O}_{2}\)

Hint:

The amide ion removes the acidic proton of ethyne and becomes ammonia.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
The hydrogen atoms of ethyne are weakly acidic because they sit on \(sp\) carbons (50 percent s-character).

Step 2: Reaction
\(\text{LiNH}_2\) is a strong base. The amide ion \(\text{NH}_2^{-}\) removes a proton from ethyne.
\(\text{HC}\equiv\text{CH}+\text{NH}_2^{-}\rightarrow\text{HC}\equiv\text{C}^{-}+\text{NH}_3\)

Step 3: Conclusion
The proton combines with the amide ion to give ammonia, so no \(\text{N}_2\), \(\text{H}_2\) or \(\text{O}_2\) is formed.

Final Answer:
The by-product (A) is ammonia gas. \[ \boxed{\text{(C) }\text{NH}_3} \]