外加磁场对乙炔气体爆炸反应影响研究

为探究磁场对气体爆炸反应的影响,实验研究了磁场强度对C₂H₂爆炸特征的影响规律,结果表明：磁场能抑制C₂H₂爆炸压力和升压速率,磁场强度越大,抑制效果越明显;沿火焰传播方向,磁场对C₂H₂爆炸火焰传播速度呈现先促进后抑制的效果,整体表现为抑制作用。磁场强度较低时,爆炸火焰平均传播速度降低了38.94%,磁场强度较高时,爆炸火焰平均传播速度降低了49.62%。利用Chemkin-Pro软件模拟了C₂H₂爆炸基元反应过程,理论推导了磁场影响C₂H₂爆炸的反应机理,磁场改变了C₂H₂爆炸反应路径,是造成爆炸特征参数下降的主要原因。由于不同种类自由基的摩尔质量和磁化强度不同,在磁场中,洛伦兹力和梯度磁场力对小分子量自由基比对大分子量自由基的作用力更大。磁场改变了自由基的运动轨迹,由于同种小分子量自由基的聚集和器壁效应的产生,减小了关键自由基之间的碰撞几率,降低了基元反应的速率,导致爆炸强度下降。

     

铝原子激发态近阈限光电离截面测量

本文利用激光烧蚀、激光泵浦-探测、共振增强多光子电离和飞行时间质谱相结合的实验技术,根据离子产额和电离激光能量的关系,获取铝原子激发态的光电离截面;并研究了光电离截面与电离富余能的依赖关系.电离富余能0-2.98 eV内光电离截面值范围为15.6±1.7 Mb-2.3±0.9 Mb,激发态的寿命为17.6±1.8,16.9±1.7ns.在光电离截面的测量中,总的均方根误差上限约为17%.     

铁氰化钆修饰电极对鸟嘌呤的电催化氧化及应用

用电化学沉积法制备了稀土铁氰化钆修饰玻碳电极(GdHCF/GC/CME),考察了该电极对鸟嘌呤的电催化氧化性能,同时根据Fenton反应产生的羟基自由基对鸟嘌呤的氧化作用和修饰电极氧化作用之间的竞争机理,对抗坏血酸清除羟基自由基进行了初步评价.实验结果表明,修饰电极对鸟嘌呤具有很好的电催化氧化性能.在HAc-NaAc缓冲液(pH=5.1)中,鸟嘌呤在1.0×10-6～4.6×10-5 mol/L浓度范围内与其氧化峰电流呈良好的线性关系,其线性回归方程为Ip(μA)=0.1112C 2.8715,r=0.9889;检出限为3.3×10-7 mol/L.以此电极评价抗坏血酸对羟基自由基的清除作用,取得了较好的效果,为羟基自由基清除剂的筛选提供了一种新的方法.     

Persistent Antimony‐ and Bismuth‐Centered Radicals in Solution

Stibinyl and bismuthinyl radicals are recognized as representative intermediates of antimony and bismuth compounds, but still elusive in the condensed phase. We successfully synthesized persistent stibinyl and bismuthinyl radicals in solution by facile dissociation of the corresponding dimers with bulky substituents. We characterized the radicals by NMR and UV/Vis spectroscopy and estimated the thermodynamic parameters for the dissociation equilibria. The radicals show n→p (HOMO→SOMO) transition bands at 497 nm (stibinyl) and 543 nm (bismuthinyl) in 3‐methylpentane and react with a stable nitroxyl radical to give the cross‐radical coupling products in good yields.     

Studies on Mechanisms and Blockade of Carcinogenic Action of Female Sex Hormones

Tumours of mice are induced by administration of Inj. Hydroxyprogesteroni Caproatis Co. (EP) in a practical subthreshold dose of carcinogenesis or 2. 5-5 times the human contraceptive dose (simply referred to as 2. 5- to 5-fold dose) combined with whole-body 0. 5 Gy gamma-ray irradiation. Malignant transformation of Syrian golden hamster embryo (SHE) cells is also induced by 5-fold dose of EP combined with 0. 3 Gy gamma-ray irradiation in vitro, thereby indicating that synergistic carcinogenesis can be obtained by combined use of physical and chemical carcinogens.The mechanisms of synergistic carcinogenesis have been further explained by cytogenetics, damage extent of the target cell DNA and production of free radicals. The Chinese traditional medicine with antioxidat-ing effect (Sulekang Capsule, SC), food additive--butylated hydroxyanisole (BHA) and green tea can effectively inhibit the carcinogenic effect of EP or EP combined with gamma rays in mice. They all have marked ability to scavenge or remove     

Effect of nitrate ions on the efficiency of sonophotochemical phenol degradation

A sonophotochemical oxidation process has been used for the treatment of an aqueous solution of phenol. The aim of this work is to evaluate the effect of nitrate ions on hydroxyl radical production and on phenol oxidation. It has been demonstrated that ultrasound can produce NOx (nitrate and nitrite), with a production rate of 2.2 μM min⁻¹. The photolysis of nitrate can significantly improve the hydroxyl radical production. The apparent rate constant for hydroxyl radical production increased from 0.0015 min⁻¹ to 0.0073 min⁻¹ while increasing initial nitrate concentration from 0 to 0.5 mM. The concentration of hydroxyl radical was directly proportional to the initial nitrate concentration. Using US/UV process, the apparent reaction rate constant of phenol degradation in the presence of nitrate reached 0.020 min⁻¹, which was relatively lower than the value obtained (0.027 min⁻¹) in the absence of nitrate. It appeared that, nitrate ions can inhibit the sonochemical degradation of organic compounds such as phenol.     

ESR spectroscopic investigation of steric and polar factors in the addition of radicals to unsaturated compounds

The rate constants of the addition of CCl₃CH₂ClCH₃(R⁶) radicals to -methyl-styrene, styrene, methyl methacrylate, methyl acrylate, and acrylonitrile and of CCl₃CH₂(CH₃)₂(R⁷) radicals to styrene, methyl acrylate, and acrylonitrile were determined by ESR spectroscopy. It was shown that the radicals R⁶ and R⁷ possess approximately equal reactivity in addition to unsaturated compounds, despite the difference in the donor-acceptor properties of the substituents at the vinyl group. In a comparison of the reactivity of radicals R⁶ and R⁷ with the reactivity of radicals CCl₃CH₂H₂(R¹), CCl₃CH₂HCH₃(R³), CCl₃CH₂HCl(R⁴), and ClCH₂CH₂Cl₂(R⁵) [1] in addition reactions, it was shown that polar and steric effects of the substituents situated in the -position to the radical site of the above-mentioned radicals, as well as the donor-acceptor properties of the substituents at the vinyl group in the unsaturated compounds, lead to appreciable changes in reactivity.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 136–141, January, 1992.     

Effect of solvation on the kinetic parameters of the reactions of phenoxyl radicals with phenols and semiquinone radicals with hydroquinones

Experimental rate constants of the reactions of semiquinone radicals with hydroquinones in chlorobenzene at ∼300 K are by almost an order of magnitude higher than the rate constants of the reactions of phenoxyl radicals with phenols, which are equivalent to the former ones by heat effects. To reveal differences in the rate constants of these groups of reactions, we performed quantum chemical calculations of the energy profiles of the reactions and dissociation energies by the B3LYP density functional theory using the GAMESS and GAUSSIAN-03 programs in the 6-31+G^* basis set. The solvation energies were calculated in all stationary points on the reaction coordinate by the method of polarized continuum model. In terms of the intersecting parabolas method, the reactions of semiquinone radicals with hydroquinones and phenoxyl radicals with phenols can be attributed to the same class of reactions only in the gas phase. In solvents this class of reactions is divided into two subclasses due to differences in solvation energies of the preliminary complexes and transition states of these reactions. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1495–1501, September, 2006.     

经由三氟甲基自由基的三氟甲基化反应研究进展

含有三氟甲基的有机分子在功能材料、农业化学品、制药等领域具有广泛应用,发展三氟甲基化的新方法是有机化学中的热点．通过产生三氟甲基自由基形成碳碳键是三氟甲基化的重要策略．本文依据三氟甲基自由基产生的不同方式,分3部分介绍三氟甲基自由基经由的碳碳键形成反应．     

Application of the electron localization function to radical systems

An application of the topological electron localization function (ELF) analysis to free radical systems is presented. A separation of the ELF function into its α‐spin and β‐spin contributions has been performed. Methyl and phenyl radicals, ortho‐, meta‐, and para‐benzyne biradicals, and their corresponding radical anions have been chosen with the aim to validate the new ELF_α and ELF_β proposed functions. The results show that the ELF separation yields complementary information about the localization of the unpaired electron. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003