alkaeneen

Alkenes, also known as olefins, are unsaturated hydrocarbons characterized by one or more carbon–carbon double bonds. In acyclic alkenes the general formula is CnH2n (n ≥ 2). The C=C bond restricts rotation, giving rise to stereoisomerism when two different substituents are attached to the double-bond carbons; common examples include cis and trans isomers. The simplest members are ethene (ethylene, C2H4) and propene (propylene, C3H6).

Nomenclature and properties follow from the double bond. Alkenes are typically nonpolar and range from gases to liquids at room temperature, with boiling points that increase with molecular size. They are more reactive than alkanes due to the unsaturated bond, readily undergoing addition reactions such as hydrogenation, halogenation, hydrohalogenation, and hydration to form alcohols.

Production and occurrence are dominated by petroleum processing and natural gas chemistry. Major industrial routes include steam cracking and catalytic cracking of larger hydrocarbons to yield lighter alkenes, and dehydrogenation of alkanes. Ethene and propene are among the most important alkenes, serving as key feedstocks for the production of plastics, solvents, and a range of chemical intermediates.

Reactions and applications focus on the reactivity of the C=C bond. Addition reactions convert alkenes into saturated products, while polymerization of ethene and propene produces polyolefins such as polyethylene and polypropylene. Alkenes also function as starting materials in the synthesis of detergents, solvents, and various specialty chemicals. Their reactivity and availability make them central to the chemical industry.