Elimination:

Definition

Alkyl halides that have a proton attached to a neighboring β-carbon atom can go through an elimination reaction to generate an alkene plus a hydrogen halide. Basically, this reaction is the opposite of the electrophilic addition of a hydrogen halide to an alkene. There are two mechanisms through which this elimination can occur - the E2 mechanism and the E1 mechanism. The E2 reaction is the very much effective for the synthesis of alkenes from alkyl halides and can be employed on primary, secondary, and tertiary alkyl halides. The E1 reaction is not specifically helpful from a synthetic point of view and takes place in competition with the S_N1 reaction of tertiary alkyl halides. Primary and secondary alkyl halides do not generally react via this mechanism.

Figure: Elimination of an alkyl halide.