mchloroperbenzoic

Meta-chloro-perbenzoic acid, commonly abbreviated MCPBA, is an organochlorine peracid widely used as an oxidizing reagent in organic synthesis. It is the meta-chloro derivative of perbenzoic acid and is typically encountered as a 77–78% solution in dichloromethane or as a dry solid. Its molecular formula is generally cited as C7H5ClO3, and it functions as a strong electrophilic oxidant in a variety of transformations.

Structure and reactivity of MCPBA derive from the peracid moiety (COOOH) attached to a meta-chlorophenyl ring. This structure enables effective transfer of oxygen in several well-known reactions, including epoxidation of alkenes, Baeyer–Villiger oxidation of ketones to esters and lactones, and oxidation of sulfides to sulfoxides (and, under some conditions, sulfones). MCPBA is valued for its relatively high selectivity and compatibility with a range of substrates, though reaction outcomes can depend on solvent, temperature, and substrate electronics.

Preparation and availability: MCPBA is commonly prepared in situ by reacting m-chlorobenzoic acid with hydrogen peroxide under acidic conditions, producing the active peracid which is frequently isolated or used as a solution in dichloromethane. Commercial suppliers also offer MCPBA as a prepared reagent, typically in chlorinated solvent or as a dry solid, with storage recommendations emphasizing protection from moisture, heat, and reducing agents.

Safety and handling: MCPBA is a strong oxidizer and can be hazardous. It is reactive and can pose explosion risks when dry or not properly handled. Procedures emphasize working in a well-ventilated area, using appropriate protective equipment, avoiding contact with incompatible materials, and storing at low temperature in air-tight containers.

See also: peracids, Baeyer–Villiger oxidation, epoxidation.