Sec 2 Preparation of alkenes Alkenes can be synthesized by the reduction of alkynes,or by the elimination of alkyl halides and alcohols. -E2 dehydrohalogenation (-HX);E1 dehydrohalogenation (-HX);Dehydration of alcohols (-H2O) Dehalogenation of vicinal dibromides(-X2) Sec 2 Preparation of alkenes Alkenes can be synthesized ❖by the reduction of alkynes, or ❖by the elimination of alkyl halides and alcohols. ◼E2 dehydrohalogenation (-HX)；E1 dehydrohalogenation (-HX)；Dehydration of alcohols (-H2O) ❖Dehalogenation of vicinal dibromides(-X2 )