自秋精达对 B.Elimination of dihalides Removal of two molecules of HX from a vicinal or geminal dihalide produces an alkyne. First step (-HX)is easy,forms vinyl halide. Second step,removal of HX from the vinyl halide requires very strong base and high temperatures. base base 一HX R- -HX (fast) R一C=C一R (slow) a vicinal dihalide vinyl halide alkyne H X base base -HX R -HX R-C- -C一R =0 (fast) (slow) R一C=C一R H X a geminal dihalide vinyl halide alkyneB. Elimination of dihalides ◼Removal of two molecules of HX from a vicinal or geminal dihalide produces an alkyne. ◼First step (-HX) is easy, forms vinyl halide. ◼Second step, removal of HX from the vinyl halide requires very strong base and high temperatures