Susceptible β-protons:

An alkyl halide can go through an elimination reaction if it has a susceptible proton positioned on a β-carbon, i.e., the carbon next to the C-X group. This proton is lost throughout the elimination reaction together with the halide ion. In a number of respects, there is a similarity here among the alkyl halides and carbonyl compounds. Alkyl halides can comprise susceptible protons at the β-position whilst carbonyl com- pounds can have acidic protons at their α-position. If we compare both of the structures, we can observe that the acidic or susceptible proton is attached to a carbon neighboring an electrophilic carbon.

Figure: Comparison of a carbonyl compound and an alkyl halide.