Reactive oxygen species in the aerobic decomposition of sodium hydroxymethanesulfinate

Sodium hydroxymethanesulfinate, (HOCH2SO2Na, HMS) is relatively stable in a queous alkaline environments, but rapidly decomposes in acidic medium to gi ve a variety of products that include sulfur dioxide. A detailed kinetic an d mechanistic study of the decomposition of HMS in slightly acidic medium h as shown a process that produces dithionite, S2O42-, which is preceded by a n induction period which persists for as long as molecular oxygen is presen t in the reaction solution. The complete consumption of molecular oxygen is a prerequisite for the formation of S2O42-. Among some of the intermediate s detected in the decomposition of HMS is the sulfite radical, SO3-. Compar isons are made between the decomposition mechanisms of thiourea dioxide (am inoiminomethanesulfinic acid) and HMS. (C) 1999 Academic Press.