Alkene formation typically occurs through the process of dehydrohalogenation, where an alkyl halide loses a hydrogen halide (like HCl or HBr) to form an alkene. This reaction often requires a strong base, which helps to remove the hydrogen atom from the carbon adjacent to the halide, resulting in the formation of a double bond between two carbon atoms. Another common method for alkene formation is elimination reactions, such as dehydration, where an alcohol loses a water molecule. This process also leads to the creation of a double bond, resulting in the formation of an alkene. Both methods are essential in organic chemistry for synthesizing various compounds.