Département de chimie moléculaire

The mechanism of chlorine dioxide (ClO2) decompn. in an alk. medium has been investigated. The formation of radicals and chlorinated species was studied in aq. solns. contg. ClO2 and simple model compds. of lignin or cellulose (vanillin, vanillyl alc., veratryl alc., methylglucoside and cellobiose) at acidic and alk. pHs. Because hypochlorite (ClO-) is an intermediate occurring in the course of the reaction mechanism, similar expts. were carried out with solns. of sodium hypochlorite (NaClO) at alk. and acidic pHs. ESR (EPR) spectroscopy based on the spin-trapping technique revealed the presence of hydroxyl radicals (HO) at alk. pH with ClO2 alone or with model compds. At the same pH, only a small amt. of HO was detected with ClO-. Chlorite (ClO2-) and chlorate (ClO3-) ions were dosed with iodometric titrns., both during ClO2 alk. decompn. and during reactions with model compds. Vanillin and vanillyl alc. were oxidized by ClO2. The intermediate ClO2- was either inert or reacted with the aldehyde function of vanillin. Cellobiose was attacked only in an alk. medium, either directly by ClO2 or indirectly by HO radicals. This resulted in the formation of glucose, which was then degraded by ClO2- ions. The generation of HO could be one reason for cellulose degrdn. by ClO2 at alk. pH, but possibly not the unique one, as it was not proved in this article, whether or not ClO2 is able to directly attach the OH functions of anhydrosugars at alk. pH. [on SciFinder(R)]