alkeners

Alkener is not a standard term in contemporary chemistry. In most references the compounds described by this name are called alkenes. An alkene is a hydrocarbon that contains at least one carbon–carbon double bond. The general formula for acyclic alkenes is CnH2n (with n ≥ 2); cyclic alkenes have the formula CnH2n−2. The double bond involves sp2-hybridized carbons and restricts rotation, which gives rise to geometric isomerism (cis/trans or E/Z) in substituted alkenes.

Alkenes occur widely in nature and industry. They are prominent components of petroleum and natural gas and are produced commercially by several methods, including catalytic dehydrogenation of alkanes, dehydration of alcohols, cracking of larger hydrocarbons, and olefin metathesis. They can also be generated by reactions such as reduction of alkynes or certain elimination processes.

The chemistry of alkenes centers on the carbon–carbon double bond, which participates in many addition reactions. Common transformations include hydrogenation, halogenation, hydrohalogenation, and hydration. Alkenes also undergo polymerization to form polymers such as polyolefins (for example, polyethylene), often under radical initiation or with specific catalysts (such as Ziegler–Natta systems).

Physical properties of alkenes vary with chain length and substitution. They are generally nonpolar and tend to be gases or liquids at room temperature for lower members, with higher boiling points for longer chains. They are flammable and typically handled with standard laboratory and industrial safety practices.

Terminology note: encountering the term alkener usually indicates a nonstandard usage referring to alkenes; the standard term to use is alkene.