peroxyacid

Peroxyacid is a class of organic acids that contain a hydroperoxy group (-OOH) attached to a carbonyl, giving the general structure R-CO-O-O-H. They act as oxidizing agents in organic synthesis by transferring an oxygen atom to substrates, often delivering electrophilic oxygen to alkenes or sulfides.

Most peroxyacids are prepared in situ by reacting a carboxylic acid with hydrogen peroxide in the presence of an acid catalyst. They are typically more reactive than the parent carboxylic acids but are also less stable, prone to exothermic decomposition. Concentrated solutions can be hazardous and require careful handling and storage away from reducing agents, light, and heat.

Common examples include peracetic acid (R = CH3), performic acid (R = H, derived from formic acid), perbenzoic acids (R = C6H5), and m-chloroperbenzoic acid (MCPBA; R = 3-Cl-C6H4). MCPBA is a widely used epoxidation reagent, valued for its efficiency and relatively clean reactions.

Applications and scope: peroxyacids are versatile oxidants in organic synthesis. They are widely used to epoxidize alkenes to give epoxides, via transfer of an oxygen from the peracid. They can also oxidize sulfides to sulfoxides and, with stronger conditions or excess reagent, to sulfones. Some peroxyacids participate in selective oxidations that are difficult with other reagents.

Safety and handling: as strong oxidizers, peroxyacids can be shock-sensitive and may decompose violently under improper conditions. They should be prepared and used in small quantities, stored refrigerated, and kept away from reducing agents, metals, and organic reducing environments.