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Published October 1992 | public
Journal Article

Free radicals and diradicals in the reaction between nitrous acid and bisulfite in acid aqueous media

Abstract

Rates of the prompt formation of (HSO_3)_2NO•(F) in the reaction of nitrous acid with bisulfite were measured by stopped-flow electron spin resonance spectrometry at pH = 3.0-5.8, 298 K. Initial rates have a positive dependence on (HONO] and [HSO_3^-] but decrease markedly with pH. The induction periods observed in air-saturated solutions are suppressed by addition of 2 mM hydroxylaminedisulfonate, (SO_3^-)_2NOH (FH), revealing a free-radical precursor to F. The spin trap 5.5-dimethyl-1-pyrroline N-oxide (DMPO) also inhibits the formation of F but without producing new paramagnetic species, ruling out monoradical intermediates. We show that these observations are consistent with the previously proposed participation of a nitrene, HON:, in this system. Present evidence suggests that the title reaction is a potential source of free radicals in natural environments.

Additional Information

© 1992 American Chemical Society. (Received: May 27, 1992) This study was financially supported by CONICET and CIC of Argentina. E. G. and L. J. P. are members of the scientific staff of CIC.

Additional details

Created:
August 20, 2023
Modified:
October 23, 2023