Metallic sodium does not react normally with :

Solution

Chemistry ma’am · 3 steps

Sodium needs an acidic hydrogen to replace. Find the one compound that has none to offer.

1. What sodium does. Sodium gives away its electron easily, so it replaces an acidic hydrogen and releases H₂ gas. Hydrogen on N, on O, or on a triple-bonded carbon is acidic enough.

   Compound	Acidic H?	Reaction with Na
   NH₃ (gas)	Yes, N–H	2Na + 2NH₃ → 2NaNH₂ + H₂ on heating
   But-2-yne, CH₃-C≡C-CH₃	No, both triple-bond carbons carry CH₃ groups	no reaction
   Ethyne, HC≡CH	Yes, H on sp carbon	2HC≡CH + 2Na → 2HC≡CNa + H₂
   tert-Butyl alcohol, (CH₃)₃COH	Yes, O–H	2(CH₃)₃COH + 2Na → 2(CH₃)₃CONa + H₂, slowly

2. Why but-2-yne fails. But-2-yne is an internal alkyne. Its C–H bonds are only on the CH₃ groups, and those sp³ hydrogens are far too weakly acidic for sodium to remove.
3. So. Sodium does not react with but-2-yne, option (b).

The idea to keep. Sodium reacts with H on N, on O, or on a terminal alkyne carbon and gives off H₂. An internal alkyne has no such hydrogen, so sodium leaves it alone.

Answer from the NTA final answer key. Solution by PrepWiser.