Preparation of alkenes

By adding $ H_2 $ to an alkyne

$H_2 $ adds to an alkyne in the presence of a palladium $Pd $ catalyst or by reacting with $ Na$ in $ NH_3 (l) $

By eliminating $H_2O $ from an alcohol

$ H_2O $ is eliminated from an alkene by →       $ H_2SO_4$ or hot $ Al_2O_3 $

By eliminating $ HX$ from a haloalkane

$ HX$ is eliminated from an alkene by hot $KOH $

Orientation:

Rule of Zaitsev The alkene where carbon atoms bearing the double bond are substituted are most favored

This rule applies only in cases where steric hindrance is low

By eliminating $X_2 $ from a dihaloalkane

$ X_2$ is eliminated from an alkene by $Zn $ or $ Mg $