Studies in homogeneous catalysis.: Radicals of the \documentclass{article}\pagestyle{empty}\begin{document}\[{\rm R}_{\rm 2}{\rm NO}^{-\bullet}\]\end{document} type as catalysts for the oxidation of methanol by cupric complexes and as promoters for various oxidations catalysed by copper

Abstract The stable radical di‐ tert ‐butyl nitroxide is found to catalyse various oxidation reactions effected by cupric complexes, and to promote various oxidations with oxygen catalysed by copper complexes. Examples of its activity are found in the formation of hydrogen cyanide from methanol, ammonia and oxygen, the synthesis of nitriles from aldehydes, ammonia and oxygen, and various catalytic oxidations of methanol to formaldehyde. The kinetics and mechanism of the oxidation of methanol by cupric‐phenanthroline, catalysed by di‐ tert ‐butyl nitroxide, have been studied in detail. The essential step in this reaction appears to be a simultaneous hydrogen abstraction (by the nitroxide radical) and electron abstraction (by the cupric ion) from coordinated methanol. The activation of C‐H bonds with respect to hydrogen abstraction in methanol and other compounds coordinated to cupric ions is discussed. The reactive cupric complexes are coordinatively unsaturated with respect to phenanthroline. The likewise unsaturated cuprous complexes formed during the oxidation regenerate the reactive cupric complexes by a fast electrontransfer reaction. This reaction gives rise to the peculiar phenomenon that the reaction rate is not a single‐valued function of the concentration of the starting‐materials, but is co‐determined by the history of the system.