Chemistry - Hydrocarbon Question with Solution | TestHub

Question Explanation:

The question asks which reagent sequence can convert a terminal alkyne, propyne (CH₃–C≡CH), into an internal alkyne, 2-butyne (CH₃–C≡C–CH₃).

Concept: Acidity of terminal alkyne, acetylide ion formation, and alkylation of alkynes (Sɴ2).

Solution:

Terminal alkynes possess an acidic hydrogen and can be deprotonated by strong bases.

CH₃–C≡CH + NaNH₂ → CH₃–C≡C⁻ Na⁺ (sodium acetylide ion)

The acetylide ion undergoes Sɴ2 alkylation with a primary alkyl halide like CH₃Cl, forming 2-butyne (CH₃–C≡C–CH₃).

CH₃–C≡C⁻ Na⁺ + CH₃–Cl → CH₃–C≡C–CH₃

Other reagent sequences listed cannot effectively generate the required acetylide ion for alkylation.

Final Answer: Option (C)