Olefines

Olefines, also known as alkenes, are unsaturated hydrocarbons containing at least one carbon–carbon double bond (C=C). They are generally represented by the formula CnH2n for acyclic monoalkenes, though cyclic alkenes have different hydrogen counts (often CnH2n−2). The carbon atoms involved in the double bond are sp2-hybridized, giving planarity around the C=C bond and enabling characteristic reactions such as electrophilic and radical additions.

Olefines are nonpolar, typically produce gases or liquids at room temperature depending on chain length, and are largely insoluble in water but soluble in many organic solvents. They can be classified as terminal (1-alkenes) where the double bond is at the end of the chain, or internal (2-alkenes and beyond). Common examples include ethene (ethylene, C2H4), propene (propylene, C3H6), and butenes (C4H8).

Production and occurrence: The most important industrial olefins are produced by refinery processes such as steam cracking of naphtha or gas oil, producing ethene and propene in particular. They are foundational feedstocks for a wide range of chemicals and polymers.

Reactions: Olefines undergo numerous addition reactions across the C=C bond, including hydrogenation to alkanes, halogenation to vicinal dihalides, hydrohalogenation, and hydration to alcohols. They readily polymerize to polyolefins (notably polyethylene and polypropylene) using radical, coordination, or Ziegler-Natta catalysis.

Industrial relevance: Olefines are among the most widely used industrial chemicals. They serve as building blocks for plastics, solvents, fuels, and various intermediate chemicals, with ethene being the single most important olefin feedstock. Safety considerations include flammability and handling under pressure, especially for light gaseous olefins.