Transient species produced in the photochemical decomposition of ceric salts in aqueous solution. Reactivity of nitrogen oxide and hydrogen compd. with oxygen and sulfur (HSO4) free radicals
Transient species produced in the photochemical decomposition of ceric salts in aqueous solution. Reactivity of nitrogen oxide and hydrogen compd. with oxygen and sulfur (HSO4) free radicals
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DOI：
10.1021/j100871a014
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发表时间：
1967-11
期刊：
影响因子：
--
通讯作者：
L. Dogliotti;E. Hayon
中科院分区：
文献类型：
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作者：
L. Dogliotti;E. Hayon
研究了硫酸铈和硝酸铈在水溶液中的闪蒸光解。硫酸铈在4550 a时产生了光吸收最大的瞬态物质，k= 6.5±1.3 X 10s M~ 1 s -1进行双分子衰变，并被分配给HSCh自由基。硝酸铈在5950a、6400 A和6750 A处产生最大值的光谱。根据该中间体在可见光区的特征吸收光谱，鉴定其为NO3自由基。发现它的衰变是一个一阶过程，k= 9.5 X 102 3sec-1。此外，还报道了一个新的紫外波段，最大波长为3350 a。硫酸盐和硝酸盐的主要初生光解过程是基于水合球向Ce （IV）离子的电荷转移：Ce (IV)-H20-到Ce (III)+ OH+ H+，然后是OH+ HS04- HS04+ OH-和OH+ HNO3-> NO3+ H20反应。这一机制的证据来自于在各种添加剂的存在下伪一阶衰变图的“零”时间的外推。HS04和X03“初始”浓度的降低与所用溶质的/c (OH+ S) X Cs值成正比。测定了HS04和XO3与甲酸酯、乙酸酯、甲醇、乙醇、2-丙醇、硫离子和铈离子等溶质的反应速率常数。HS04被发现是比X03更强的氧化剂，尽管HS04没有OH自由基那么强。
The flash photolysis of ceric sulfate and ceric nitrate in aqueous solutions was studied. Ceric sulfate produced a transient species with an optical absorption maximum at 4550 A which decays bimolecularly with k= 6.5±1.3 X 10s M~ l sec-1 and is assigned to the HSCh free radical. Ceric nitrate gave rise to an optical spectrum with maxima at 5950, 6400, and 6750 A. This intermediate was identified as the NO3 radical by its characteristic absorption spectrum in the visible region. It was found to decay by a first-order process with k= 9.5 X 102 3sec-1. In addition, a new ultraviolet band with maximaat 3350 A is reported. The main primary photolytic process in both sulfate and nitrate salts is explained on the basis of a charge transfer from the hydration sphere to the Ce (IV) ion: Ce (IV)-H20-t Ce (III)+ OH+ H+, followed by reactions OH+ HS04- HS04+ OH-and OH+ HNO3-> NO3+ H20. Evidence for thismechanism was derived from the extrapolation to “zero” timeof the pseudo-first-order decay plots in presence of various additives. The decrease of the “initial” concentration of HS04 and X03 produced was found to be proportional to the/c (OH+ S) X Cs values of the solutes used. The rate constants for the reaction of HS04 and XO3 with added solutes—formate, acetate, methanol, ethanol, 2-propanol, thallous ions, and cerous ions—were obtained. HS04 is found to be a stronger oxidizing agent than X03 although HS04 is not as strong as OH radicals.