Oxiranen

Oxiranen, also known as oxiranes or epoxides, are a class of organic compounds that contain a three-membered ring consisting of two carbon atoms and one oxygen atom. The simplest member is oxirane, commonly called ethylene oxide (C2H4O). The small ring imparts substantial ring strain, which makes oxiranes unusually reactive toward nucleophilic ring-opening and related transformations.

Preparation and occurrence: Ethylene oxide is produced industrially by catalytic oxidation of ethylene with oxygen, typically over silver catalysts. More generally, epoxides can be prepared by epoxidation of alkenes with peracids (the Prilezhaev reaction) or by cyclization of halohydrins under basic conditions. Substituted oxiranes (glycidyl systems) arise in many synthetic routes and are common intermediates in polymer and pharmaceutical chemistry.

Reactions: A defining feature of oxiranes is their susceptibility to nucleophilic ring opening. Under acidic conditions, attack tends to occur at the more substituted carbon; under basic or neutral conditions, attack occurs at the less substituted carbon. Ring opening with water yields glycols; with alcohols yields beta-alkoxy alcohols; with amines yields beta-amino alcohols. Oxiranes can undergo polymerization to form polyether resins; glycidyl ethers are widely used as precursors to epoxy resins for coatings, adhesives, and composites.

Applications: Oxiranes are versatile intermediates in organic synthesis. Ethylene oxide is a major industrial chemical used to produce ethylene glycols, solvents, and surfactants. Propylene oxide and other substituted oxiranes serve as precursors to polyether polyols, epoxy resins, and various fine chemicals.

Safety: Epoxides are reactive and can be hazardous. Many oxiranes are irritants and toxic; ethylene oxide is flammable and classified as a carcinogen. Proper handling, ventilation, and protective equipment are essential in their use and storage.