Epoxiden

Epoxiden, or epoxides, are a family of cyclic ethers characterized by a three-membered ring containing one oxygen atom, commonly referred to as an oxirane ring. The ring is typically drawn as a triangle with two carbon atoms and an oxygen. Substituents on the ring vary, giving a wide range of compounds. The ring strain in the oxirane makes epoxides reactive toward nucleophiles and acids, leading to ring-opening reactions that are widely exploited in synthesis.

Epoxiden are usually prepared by epoxidation of alkenes, using oxidants such as meta-chloroperoxybenzoic acid (m-CPBA) or by catalytic methods using hydrogen peroxide. They can also be formed intramolecularly from halohydrins under basic conditions.

In organic synthesis, epoxiden undergo ring opening with nucleophiles including water, alcohols, and amines. The conditions influence regioselectivity: acid-catalyzed openings favor attack at the more substituted carbon, while base-catalyzed openings favor the less substituted carbon. Epoxiden are also monomers or functional groups in polymer chemistry, notably in epoxy resins formed from multiepoxide monomers with hardeners such as amines or acids. The resulting polymers are used in coatings, adhesives, composites, and electronics potting.

Safety and handling: epoxiden range from relatively modest to highly hazardous; many are irritants, and some small-molecule epoxides (for example ethylene oxide) are toxic and carcinogenic, requiring appropriate controls.