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Epoxidation of Alkenes with Peracids

Epoxidation of Alkenes with Peracids: Introduction

Reaction principle

During the epoxidation of alkenes, an oxygen atom is transferred from the peracid to the C=C double bond thus forming an oxirane ring. Since the transferred oxygen atom carries a positive charge, peracids must be considered electrophilic oxidizing agents. In the laboratory, the epoxidation agent of choice is m-chloroperbenzoic acid (MCPBA). Other peracids used are peroxybenzoic acid and peroxyacetic acid. The latter is prepared in situ from acetic acid and hydrogen peroxide. In addition to peracids, tert-butyl hydroperoxide (TBHP), dioxirane and alkaline hydrogen peroxide are frequently used .

Example

Fig.1

The reaction of alkenes with peracids is often called the Prilezhaev (Prileschajew) reaction.

Applications

Because of its wide utility, epoxidation is one of the most frequently used reactions in organic chemistry. Starting with epoxides, 1,2-diols and a large number of other 1,2-functionalized compounds can be synthetized. Epoxides, particularly epichlorohydrin, are used in the preparation of epoxy resins, a group of adhesives. Polymerization of epoxides gives polyethylene glycols or polyoxoalkylenes which, depending on their molecular weights, are used as detergents, lubricants, waxes, and components in hydraulic liquids.

Biological significance

Epoxidation plays an important role in the metabolism of condensed aromatic hydrocarbons in animal organisms. The enzyme catalyzed epoxidation of the triterpene squalene is an important step in the biosynthesis of steroids.

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