Generation of nitroxyl radicals in reactions of nitrogen dioxide with p-benzoquinones

Abstract

The formation of oxynitroxyl radicals has been observed by EPR in the course of exposure of p-benzoquinones to nitrogen dioxide. This process involves addition of nitrogen dioxide to the double bond system of quinones. Thermal conversion of oxynitroxyl radicals lead to the formation of acyl(alkyl)nitroxyl and iminoxyl radicals along with molecular nitration products. Kinetics of the oxynitroxyl radical formation depending on the nitrogen dioxide pressure has been defined. The temperature dependence of stationary concentrations of oxynitroxyl radicals at 230–310 K is determined by the equilibrium between the monomer and dimer forms of nitrogen dioxide. Nitrogen tetraoxide was found to initiate radical formation in p-benzoquinones.