Epoxide

The epoxides and epoxides, after the Hantzsch - Widman system oxiranes or by replacement nomenclature Oxacyclopropane are a chemical substance group very reactive, cyclic organic compounds. They form a three-membered ring in which a carbon is replaced by an oxygen atom in comparison to the cyclopropane. Epoxide thus form the simplest oxygen-containing heterocycles. The oxygen atom is referred to as epoxy bridge.

Representative

The simplest and technically interesting epoxide is ethylene oxide ( ethene oxide ). It is produced by the oxidation of ethylene over a silver catalyst (heterogeneous catalysis ). Because of prevailing in a three-ring ring voltage ( about 115 kJ / mol), the ring can be opened easily by a nucleophilic attack on a carbon atom. The oxygen atom of the epoxide ring is in this reaction, although the leaving group, but is connected to a carbon atom of the epoxide and is thus still present in the molecule.

If one or ( etc. alkyl radicals, aryl radicals, alkaryl radicals ) are replaced more hydrogen atoms of the ethylene oxide by organyl radicals are more representative of the group of substances oxiranes.

A polymer of several epoxy segments is a polyepoxide, and epoxy resin. These are used as adhesives or composites.

Epoxides are intermediates in the production of the flu drug oseltamivir (Tamiflu ) from shikimic acid contained in Japanese star anise.

Some epoxy resins ( eg, bisphenol A diglycidyl ether and -F) are high-grade allergens in terms of labor, especially that are exposed directly in production (eg in the manufacture of aircraft or modern wind turbines ).

Formation by epoxidation of a double bond

Epoxides can be formed at room temperature by the reaction of an alkene and a peroxycarboxylic acid. Next the epoxide is produced a carboxylic acid.

Often referred to as peroxycarboxylic acid meta -chloroperbenzoic acid ( MCPBA ) is used as this is in contrast to other percarboxylic relatively stable and safe to handle. Other percarboxylic acids, which can be used for epoxidation are peroxyformic acid and peroxyacetic acid. However, these are only produced during the reaction of formic acid or acetic acid and hydrogen peroxide ( in situ process).

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