Different channels of ·OH radical reaction with tryptophanol in aqueous solutions: A pulse radiolysis study

The pulse radiolysis technique has been employed to study the reaction of ·OH radical with tryptophanol (TPN). Reactions of specific one-electron oxidants like Br₂· - and N₃· and ·H atom were carried out to understand the contribution of different channels of · OH radical reaction with TPN. The studies were carried out in the pH range 3 to 10. One-electron oxidation of TPN (pH 3) produced radical cation absorbing at 570 nm. However, at higher pH, deprotonation of TPN cation radical takes place from N(1) position and indolyl radical absorbing at 520 nm with a p ^K a value of 3.6 is formed. Redox titration with TMPD, ABTS^2- and MV²⁺ was performed to determine the total yield of oxidizing and reducing radicals produced during ·OH reaction.     

.OH诱导氧化磷酰化甲硫氨酸机理的脉冲辐解研究

采用脉冲辐解动态吸收光谱研究了.OH自由基诱导N-二异丙基磷酰化甲硫氨酸(NDM)水溶液的氧化过程, 结果表明.OH主要进攻NDM中硫原子, 并形成含硫三电子键NDM2^+[S], 其在480nm处有最大吸收峰, 形成和衰变均呈一级反应, 推导了反应机理,并与.OH自由基诱导氧化甲硫氨酸水溶液机理进行了比较。     

A kinetic, spectral and theoretical investigation on the role of oxygen in the radiolytic oxidation of a sorbityl cyclic acetal

The oxidation process of the cyclic acetal sorbitylfurfural (SF) has been thoroughly examined from the kinetic, spectroscopic and theoretical point of view. Oxidation has been initiated by the radiolitically produced OH radical in the presence of variable oxygen amounts. Two competing reaction pathways are evidenced which lead to quite different products, although they do not affect the acetal ring integrity. The peroxidation of the hydroxylated furanic ring (k ₄=(6.1±0.9)×10⁸ M⁻¹ s⁻¹) maintains the ring structurevia HO₂^• elimination (k ₆=(1.9±0.4)×10⁵ s⁻¹). Unlike that, the peroxidation of the pseudo-allylic radical (k ₅=(1.9±0.9)×10⁹ M⁻¹ s⁻¹), formedvia β-cleavage, fixes the destructured intermediate, leading to a tetroxide, which slowly decomposes through a Russell mechanism (k ₈=(2.3±0.6)×10² s⁻¹). It is confirmed that the steady state concentration of the tetroxide is very low, which suggests a molar absorption coefficient for it around 1.2×10⁴ M⁻¹ cm⁻¹ at 265 nm. The end products of the latter pathway have been characterized as carboxylic and butenald-sorbitol derivatives. The kinetic and spectral data of every step of the process have been fitted by the above outlined mechanism. The energetics of the mechanism has been detailed byab initio computations as well, carrying further substantiation to it. Semi-empirical calculations were also employed to describe the spectral properties of each intermediate.     

在血卟啉衍生物光敏体系中DMPO捕集自由基的ESR研究

光照血卟啉衍生物(HPD)用于肿瘤的诊断和治疗已取得很大的成效,对此药理过程的分子机理的探索也开始引起生物和化学工作者的重视.我们的实验表明,在HPD光敏体系中自由基起着重要作用,特别是羟基自由基可能是HPD光致杀伤肿瘤细胞的主要原因.HPD光敏过程所产生的自由基的寿命极短,用化学方法或用一般ESR直接检测非常困难,但可被     

氟烷基化和氟烷氧基化的研究 32. 铜存在下氟砜基二氟碘甲烷与烯烃的反应─一个电子转移引发同时存在自由基和卡宾的过程

在催化量的铜粉存在下, 氟砜基二氟碘甲烷在DG、乙酐或不加溶剂时与烯烃反应,得到加成产物(3,4)和三元环产物。对反应机理作了初步探讨, 3,4经自由基加成得到而三元环产物是涉及二氟卡宾中间体。     

Observed and calculated 1H and 13C chemical shifts induced by the in situ oxidation of model sulfides to sulfoxides and sulfones

A series of model sulfides was oxidized in the NMR sample tube to sulfoxides and sulfones by the stepwise addition of meta‐chloroperbenzoic acid in deuterochloroform. Various methods of quantum chemical calculations have been tested to reproduce the observed ¹H and ¹³C chemical shifts of the starting sulfides and their oxidation products. It has been shown that the determination of the energy‐minimized conformation is a very important condition for obtaining realistic data in the subsequent calculation of the NMR chemical shifts. The correlation between calculated and observed chemical shifts is very good for carbon atoms (even for the ‘cheap’ DFT B3LYP/6‐31G* method) and somewhat less satisfactory for hydrogen atoms. The calculated chemical shifts induced by oxidation (the Δδ values) agree even better with the experimental values and can also be used to determine the oxidation state of the sulfur atom (? S? , ? SO? , ? SO₂? ). Copyright © 2010 John Wiley & Sons, Ltd.     

Stabilization of tautomeric forms P(OH)3 and HP(OH)2 and their derivatives by coordination to palladium and nickel atoms in heterometallic clusters with the Mo3MQ44+ core (M = Ni, Pd; Q = S, Se)

The cluster aqua complexes [Mo₃(MCl)Q₄(H₂O)₉]³⁺ (M = Pd or Ni) in hydrochloric acid solutions induce isomerization of the hydrophosphoryl compounds (HO)₂P(O)H, (HO)P(O)H₂, PhP(O)(OH)H, and Ph₂P(O)H into the hydroxo tautomers P(OH)₃, HP(OH)₂, PhP(OH)₂, and Ph₂P(OH), which are stabilized by coordination of the phosphorus atom to the Pd or Ni atoms. The reactions were studied by ³¹P NMR and UV-Vis spectroscopy. The kinetics of the reactions of phosphorous acid with [Mo₃(PdCl)Q₄(H₂O)₉]³⁺ was investigated by spectrophotometry. The [Mo₃(Pd(PhP(OH)₂))S₄(H₂O)₂Cl₇]³⁻ complex was isolated as a supramolecular adduct with cucurbit [8]uril, and the [Mo₃(Ni(P(OH)₃))S₄(H₂O)₈Cl]³⁺ complex was isolated as an adduct with cucurbit [6]uril. The structures of both compounds were established by X-ray diffraction analysis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 606–613, March, 2005.