Alkene stability is determined by three major factors: degree of substitution, cis-trans isomerism and whether the alkene is conjugated or isolated. The stability of alkenes is important as they are the starting material for many different chemicals and are widely used in the chemical industry.
Alkenes are generally more stable if they are more highly alkylated, are in the trans double bond configuration and are conjugated rather than isolated. Examples of common alkenes include ethene and propene, both used in the polymers polyethylene and polypropylene. These are both fundamental to the manufacture of common plastics. Zaitsev's rule is applied to predict the most stable alkene in elimination reactions.