Time-Resolved Fluorescence and Transient Spectroscopy in Determining Photochemical and Photophysical Channels in Reacting Systems in Solutions and Microheterogeneous Media
作者:David G. Whitten、Mohammad S. Farahat、Elizabeth R. Gaillard
DOI:10.1111/j.1751-1097.1997.tb01873.x
日期:1997.1
amphiphiles that readily form bilayer systems in aqueous media has been analyzed using a distribution of lifetimes analysis (DLA). The utility of DLA for quantitative studies was first determined by simulation of artificial decay data. Despite some limitations in DLA, qualitative conclusions as to the nature of the fluorescing species may be drawn when supplementary information such as steady‐state spectroscopic
摘要:已使用时间分辨光谱技术对均质和微异质系统中的短寿命中间体进行表征。从这些技术中获得的数据已经以一种相对非常规的方式进行了分析,以阐明两个反应系统的复杂瞬态行为。已经使用寿命分布分析 (DLA) 分析了一系列易于在水性介质中形成双层系统的 fraws-芪衍生的两亲物的高度非指数荧光衰减。DLA 用于定量研究的效用首先是通过模拟人工衰减数据来确定的。尽管 DLA 存在一些限制,当还考虑诸如稳态光谱数据之类的补充信息时,可以得出关于荧光物质性质的定性结论。结果表明,观察到的荧光来自不同类型的激发态物质,这些物质由两个或多个反式二苯乙烯单元组成;其中一个排放归因于基态聚集体的激发态,而另一个归因于可能由双层中的“缺陷”引起的准分子。衰变的非指数性质归因于荧光物质所经历的环境分布。已经发现溶液中几种激发的频哪醇和四氯化碳之间的电子转移 (ET) 反应产生的产物的量子产率在氧气存在下高于 1,提
Oxidation of Ferrous and Ferrocyanide Ions by Peroxyl Radicals
作者:G. I. Khaikin、Z. B. Alfassi、R. E. Huie、P. Neta
DOI:10.1021/jp9533335
日期:1996.1.1
Alkylperoxyl and arylperoxyl radicals were produced by pulseradiolysis in aqueous solutions, and their reactions with ferrous and ferrocyanide ions were studied by kinetic spectrophotometry. Oxidation of Fe(CN)64- took place with rate constants that varied from <1 × 105 to 5 × 107 L mol-1 s-1, depending on the electron-withdrawing effects of the substituents on the peroxyl radical and presumably reflecting
在水溶液中通过脉冲辐射分解产生烷基过氧自由基和芳基过氧自由基,并通过动力学分光光度法研究它们与亚铁和亚铁氰化物离子的反应。Fe(CN)6 4-的氧化速率常数从<1×10 5到5×10 7 L mol -1 s -1变化,这取决于取代基对过氧自由基和电子的吸电子作用。大概反映了过氧自由基还原电位的变化,这是外球电子转移所期望的。Fe aq 2+的氧化另一方面,是通过受水配体的解离交换速率控制的内球机理发生的。所述速率常数分别为几乎相同的所有过氧自由基检查(ķ =(0.5-1.1)×10 6大号摩尔-1小号-1)和所涉及的瞬时中间体的形成,RO 2 -的Fe 3+,后来分解产生Fe aq 3+。H +和Fe 2+促进分解。所提出的机理是对先前提出的反应方案的修改。
Electron-Beam Decomposition of Carbon Tetrachloride in Air/Nitrogen
作者:Koichi Hirota、Hidehiko Arai、Shoji Hashimoto
DOI:10.1246/bcsj.73.2719
日期:2000.12
Carbon tetrachloride (CCl4, approximately 10, 50, and 100 ppm) in air and nitrogen was irradiated with electron beams in both the presence and absence of water. The absorbed doses ranged from 1.2 to 18.0 kGys. An absorbed dose of 18 kGy led to approximately 90% decomposition of CCl4 at a concentration of 10 ppm in dry air. The presence of water lowered the decomposition rate in air by 20%, but not in nitrogen. Negative oxygen ions (O2-) formed upon the irradiation of wet air played a role in the oxidation of CCl4. Water molecules became negative cluster ions (O2-(H2O)n) with negative oxygen ions, which depressed the oxidation.
CCl3OO˙ radicals are shown to oxidize three equivalents of iodide ions to yield one I2 molecule (showing up as I3– in aqueous solution) and one I˙ atom (showing up as I2˙–) per peroxyl unit; the mechanism is considered to proceed via a protonated CCl3OO˙I– adduct radical as the primary intermediate and subsequent nucleophilic (SN2) attack by a second iodide accompanied by electron localization in the hydroperoxide moiety leads to I2 and CCl3O˙ with the latter being responsible for the oxidation of the third iodide.
Kinetics and Mechanisms of the Self-Reactions of CCl<sub>3</sub>O<sub>2</sub> and CHCl<sub>2</sub>O<sub>2</sub> Radicals and Their Reactions with HO<sub>2</sub>
作者:Valéry Catoire、Robert Lesclaux、William F. Schneider、Timothy J. Wallington
DOI:10.1021/jp960572z
日期:1996.1.1
trends in the reactivity of chloromethyl peroxy radicals are discussed. As part of this work, the following reaction rate constants were measured (units of cm3 molecule-1 s-1) at roomtemperature: k(CCl3O2 + CH3O2) = (6.6 ± 1.7) × 10-12, k(Cl + CHCl3) = (1.1 ± 0.1) × 10-13, k(Cl + CH2Cl2) = (3.5 ± 0.4) × 10-13, k(Cl + CHClO) = (7.0 ± 1.0) × 10-13, and k(F + CHCl3) = (5.4 ± 1.5) × 10-12.
反应的动力学和机理CCl 3 O 2 + CCl 3 O 2 →2CCl 3 O + O 2(1),CHCl 2 O 2 + CHCl 2 O 2 →2CHCl 2 O + O 2(2a),CHCl 2 O 2 + CHCl 2 O 2 →CHCl 2 OH + CCl 2 O + O 2(2b),CCl 3 O 2 + HO 2 →产物(3)和CHCl 2 O 2 + HO在总压力为700-760托时,研究了2 →产物(4)与温度的关系。使用了两种补充技术:用于动力学测量的快速光解/紫外吸收和用于最终产品分析的连续光解/ FTIR光谱。在220至280nm之间测定CHCl 2 O 2和CCl 3 O 2的紫外吸收光谱;它们的形状类似于其他烷基过氧自由基,但具有较宽和较弱的谱带。由氯原子在氯原子引发的氯原子氧化链中CCl 2 O的形成速率确定速率常数k 1在273和460 K之间,其中反应1是限速步骤;k