Phosphorous and hypophosphorous acid derived radicals and their reactionsùan E.P.R. study

Abstract

The radicals HPO₂-, HPO₃-, and PO₃^2- can be generated in aqueous solution by interaction of Ti¹¹¹ and hydrogen peroxide with hypophosphorous and phosphorous acids in the flow cell of an e.p.r. spectrometer. Their spectral parameters indicate that each of these radicals has a pyramidal structure. Radicals formed by addition of HPO₂-, HPO₃-, and PO₃^2-, to unsaturated compounds are characterized by large ³¹P hyperfine splitting constants. The delocalization of the unpaired electron is tentatively attributed to interaction of the half-filled p-orbital with phosphorus 3d orbitals. Reduction of iodo and bromo compounds with HPO₂-, HPO₃-, and PO₃^2- gives high stationary concentrations of alkyl radicals. Benzenediazonium ion is similarly reduced to phenyl radical, and biacetyl to its semidione.