Preparation of Alkynes:Elimination Reactions of Dihalides ■ Treatment of a 1,2 dihaloalkane with KOH or NaOH produces a two-fold elimination of HX ■ 1,2-dihaloalkanes are made from addition of Br2 or Cl2 to an alkene HC ■Intermediate is 1.2 NaNH2 2.Hg0+ CHC=CCH,OH a vinyl halide C CH2OH 2-Butyn-1-ol (85%) 3-Chloro-2-buten-1-ol (a vinvlic chloride) Br H B型 1,2-Diphenylethylene (Stilbene) 1-Dticina)thane 2 KOH,ethanol C=C- +2H2O+2B Diphenylacetylene(85%)Preparation of Alkynes: Elimination Reactions of Dihalides „ Treatment of a 1,2 dihaloalkane with KOH or NaOH produces a two-fold elimination of HX „ 1,2-dihaloalkanes are made from addition of Br 2 or Cl 2 to an alkene „ Intermediate is a vinyl halide