Alkynes can be prepared from vicinal dihalides via a double dehydrohalogenation process. Which of th — Hydrocarbons Chemistry Question

💡 Solution & Explanation

To remove two molecules of $HX$ from a vicinal dihalide, a strong base is required. A common laboratory method is treating the dihalide first with alcoholic $KOH$ to remove one $HX$ molecule (yielding a less reactive vinyl halide), and then using a much stronger base, like sodamide ($NaNH_2$), to force the second elimination. Alternatively, an excess of strong base like $NaNH_2$ can achieve double elimination in one pot. Zinc dust performs dehalogenation (removing $X_2$ from vicinal dihalides to give alkenes, or tetrahalides to give alkynes), but not dehydrohalogenation.