One of the principal methods for alkene synthesis in the laboratory is the elimination of alkyl halides, alcohols and similar compounds.
When an alkyl halide is used, the reaction is called a dehydrohalogenation.
Alkenes can be synthesized from alcohols via dehydration, in which case water is lost. For example, the dehydration of ethanol produces ethene:
C2H5OH --> C2H4 + H2O