Z. B. Alfassi

On the reactions of CO−3 radicals with NOx radicals

Abstract The reactions of CO − 3 radicals with NO x radicals were studied by pulse radiolysis of deoxygenated aqueous solutions containing carbonate and nitrate ions. The OH radicals react with carbonate to yield CO − 3 and the e − aq reacts with nitrate to yield NO 2− 3 , which then converts into NO 2 . This conversion has a rate constant of 4.6×10 4 s −1 in alkaline solutions but is catalyzed by HCO − 3 ( k =2.8×10 7 L mol −1 s −1 ). The CO − 3 radicals react rapidly with both NO 2− 3 ( k =1.0×10 9 L mol −1 s −1 ) and NO 2 ( k =4.6×10 8 L mol −1 s −1 ). The expected combination product was short lived and was not observed on the microsecond time scale and the possible peroxynitrite product was not detected following γ -radiolysis. A similar study with solutions containing carbonate and nitrite shows that NO 2− 2 reacts with CO − 3 faster than NO 2− 3 and NO reacts with CO − 3 faster than NO 2 .

Kinetics of one-electron oxidation by the ClO radical

Pulse radiolysis studies were carried out to determine the rate constants for reactions of ClO radicals in aqueous solution. These radicals were produced by the reaction of OH with hypochlorite ions in N2O saturated solutions. The rate constants for their reactions with several compounds were determined by following the build up of the product radical absorption and in several cases by competition kinetics. ClO was found to be a powerful oxidant which reacts very rapidly with phenoxide ions to form phenoxyl radicals and with dimethoxybenzenes to form the cation radicals (k = 7 × 108 −2 × 109 M-1 s-1). ClO also oxidizes ClO-2 and N-3 ions rapidly (9.4 × 108 and 2.5 × 108 M-1 s-1, respectively), but its reactions with formate and benzoate ions were too slow to measure. ClO does not oxidize carbonate but the CO-3 radical reacts with ClO- slowly (k = 5.1 × 105 M-1 s-1).