From alcohols: R-OH HX.R-X From other halides R-X +X →R-X+X Reactions of Alkyl Halides The alkyl halides are chemically versatile. The halogen atom may leave with its bonding pair of electrons to give a halide ion which is stable-a halide is called a good leaving group If an atom replaces the halide the overall reaction is a substitution. If the halide loss is accompanied by the loss of another atom,the overall reaction is called an elimination Very often the other atom lost is a hydrogen(as H).The elimination of H-X is common,and is called a dehydrohalogenation. Often substitution and elimination reactions will occur in competition with each other. Ch06 Alkyl Halides (landscape) Page 7Ch06 Alkyl Halides (landscape) Page 7 From alcohols: From other halides: Reactions of Alkyl Halides The alkyl halides are chemically versatile. The halogen atom may leave with its bonding pair of electrons to give a halide ion which is stable – a halide is called a good leaving group. If an atom replaces the halide the overall reaction is a substitution. If the halide loss is accompanied by the loss of another atom, the overall reaction is called an elimination. Very often the other atom lost is a hydrogen (as H+ ). The elimination of H-X is common, and is called a dehydrohalogenation. Often substitution and elimination reactions will occur in competition with each other. R OH H-X R X R X' + X R X - + 'X -