Addition Preparation of Alkenes G=0 X-Y Elimination Dehydrohalogenation elimination of HX from alkyl halide-use strong base and heat H H KOH CH3CH2OH KBr H2O H Bromocyclohexane Cyclohexene(81%) Dehydration elimination of H-OH from an alcohol-require strong acids (sulfuric acid,50 C) CH3 CHs OH HS04,H20 THF,50C +H20 1-Methylcyclohexanol 1-Methylcyclohexene (91%)Preparation of Alkenes Dehydrohalogenation „elimination of HX from alkyl halide – use strong base and heat Dehydration „ elimination of H-OH from an alcohol - require strong acids (sulfuric acid, 50 ºC)