水合烟酸钡的合成、±结构表征和热化学性质

选择烟酸和氢氧化钡作为反应物, 利用室温固相合成方法, 借助于球磨技术, 合成了一种新的化合物——水合烟酸钡. 利用化学分析、元素分析、FTIR和X射线粉末衍射等方法确定了它的组成和结构为Ba(Nic)2·3H2O(s). 利用精密自动绝热热量计直接测定了此化合物在78-400 K温区的摩尔热容. 在热容曲线上出现了一个明显的吸热峰, 通过对热容曲线的解析, 得到了相变过程的峰温、相变焓和相变熵分别为(327.097±1.082) K、(16.793±0.084) kJ·mol-1和(51.340±0.164) J·K-1·mol-1. 将该温区的摩尔热容实验值用最小二乘法拟合得到摩尔热容(Cp,m)对温度(T)的多项式方程, 并且在此基础上计算出了它的舒平热容值和各种热力学函数值. 另外, 依据Hess定律, 通过设计合理的热化学循环, 选择体积为100 mL、浓度为0.5 mol·L-1的盐酸作为量热溶剂, 利用等温环境溶解-反应热量计分别测量固相反应的反应物和产物在所选溶剂中的溶解焓, 利用溶解焓确定固相反应的反应焓为⊿rH0m=-(84.12±0.38) kJ·mol-1. 最后, 利用固相反应的反应焓和其它反应物和产物已知的热力学数据计算出水合烟酸钡的标准摩尔生成焓为⊿fH0m[Ba(Nic)2·3H2O(s)]=-(2115.13±1.90) kJ·mol-1.     

去氢枞酸异丙醇胺衍生物的合成及其细胞毒性评价

为了寻找高效的抗肿瘤活性化合物,设计合成了一系列去氢枞酸异丙醇胺类化合物,利用IR、NMR和MS对其结构进行表征。采用噻唑蓝(MTT)法评价了目标化合物对四种不同肿瘤细胞T24(人膀胱移行癌细胞)、HepG2(人肝癌细胞)、SK-OV-3(人卵巢癌细胞)、A549(人肺癌细胞)和LO2(人正常肝细胞)的抗增殖活性。结果表明,部分化合物对肿瘤细胞的抑制作用优于阳性对照顺铂。其中,化合物3d对四种细胞株表现出最好的抗增殖效果,IC₅₀值分为8.10±0.28,8.65±0.10,13.21±0.35和8.24±0.42 μmol.L_-1^{。初步机理研究表明},化合物3d使A549细胞周期阻滞在G1/G0期,并诱导A549细胞凋亡,且呈浓度依赖性。     

2种偶氮席夫碱类化合物的合成及其热致变色性质

通过重氮偶合反应制得2种氨基偶氮化合物在经纯化下燥后,与水杨醛的乙醇溶液在60℃反应4 h分别得到2种偶氮席夫碱类目标化合物,通过元素分析、核磁共振氢谱、红外光谱测试技术表征了其结构.紫外光谱测试化合物在DMSO溶液的紫外吸收,在升温速率为1.5℃/min测试时,化合物A和B紫外吸收表现出热致变色性质;在45℃的恒定温度测试时,化合物A在450和348 nm的吸光度值与时间呈线性关系,化合物B在425和356 nm的吸光度值与时间呈线性关系.研究表明,2种偶氮席夫碱类化合物有良好的热致变色性,是性能良好的热致变色材料.     

甲基红-H2O2-HRP伏安酶联免疫分析法测定HRP及其标记物

提出了一种新的辣根过氧化物酶的底物-甲基红,它本身具有电化学活性,能够在静汞电极上发生还原反应,产生灵敏的伏安电流信号.以H2O2为氧化剂,HRP能催化氧化还原反应的发生,使甲基红被氧化分解,其平衡浓度降低,对应的还原峰电流降低,峰电流的降低值与HRP的质量浓度在5.0×10-8～5.0×10-7g/mL之间呈线性关系,对2.0×10-7g/mL HRP进行11次测定的相对标准偏差为4.6%,方法的检出限为1.8×10-8g/mL.应用于IgG-HRP和Avidin-HRP的测定.     

C2H3＋NO2反应速率常数的研究

利用激光光解C2H3Br产生C2H3自由基,在气相298 K, 总压2.66×103 Pa的条件下,研究C2H3与NO2的反应,用激光光解-激光诱导荧光（LP-LIF）检测中间产物OH自由基的相对浓度随着反应时间的变化关系,报导了双分子反应C2H3＋NO2的速率常数k(C2H3＋NO2)=(1.8±0.05)×10－11cm3•molec.－1•s－1,同时也得到OH＋NO2反应的速率常数k(OH＋NO2)=(2.1±0.15)×10－12 cm3•molec.－1•s－1.     

·OH自由基与CH3CN反应机理及动力学

在CBS-QB3水平上研究了CH3CN 和·OH反应的势能面, 其中包括两个中间体和9个反应过渡态. 分别给出了各主要物质的稳定构型、相对能量及各反应路径的能垒. 根据计算的CBS-QB3势能面, 探讨了CH3CN+·OH反应机理. 计算结果表明, 生成产物P1(·CH2CN+H2O)的反应路径在整个反应体系中占主要地位. 运用过渡态理论对产物通道P1(·CH2CN+H2O)的速率常数k1(cm3·molecule-1·s-1)进行了计算. 预测了k1(cm3·molecule-1·s-1)在250-3000 K温度范围内的速率常数表达式为k1(250-3000 K)=2.06×10^-20T^3.045exp(-780.00/T). 通过与已有的实验值进行对比得出, 在实验所测定的250-320 K 范围内, 计算得到的k1的数值与已有的实验值比较吻合. 由初始反应物生成产物P1 (·CH2CN+H2O)只需要克服一个14.2 kJ·mol-1的能垒. 而产物·CH2CN+H2O生成后要重新回到初始反应物CH3CN+·OH, 则需要克服一个高达111.2 kJ·mol-1的能垒,这就表明一旦产物P1生成后就很难再回到初始反应物.     

铈配合物参与的光催化环醇类化合物碳-碳键断裂官能团化反应

正醇类化合物的碳-碳键官能团化反应一直是有机化学家们关注的焦点之一.由于醇类化合物O—H键键解离能比较高,约为440 k J/mol,使醇类化合物发生碳-碳键断裂并进行直接官能团化反应的方法目前在文献中还鲜有报道.上海科技大学物质科学与技术学院左智伟课题组利用可见光催化的方法,顺利地实现了环醇类化合物的     

粒度对多相反应动力学参数的影响

以纳米氧化锌与硫酸氢钠溶液为反应体系, 研究反应物粒度对动力学参数的影响规律. 讨论了表观活化能降低的原因. 结果表明：当反应物粒径、反应温度和搅拌速率一定时, 纳米氧化锌与硫酸氢钠溶液的反应速率仅与反应物的浓度有关；反应物粒度对多相反应的反应级数、速率常数、表观活化能和指前因子均有较大的影响；随着反应物粒径的减小, 表观活化能和指前因子减小, 而反应级数和速率常数增大, 并且速率常数和表观活化能与反应物粒径的倒数呈线性关系；反应物粒度是通过摩尔表面积、摩尔表面能和摩尔表面熵三个方面影响多相反应的动力学参数的.     

粒度对纳米氧化镍与硫酸氢钠水溶液反应动力学的影响

以纳米氧化镍与硫酸氢钠水溶液为反应体系,研究了不同粒度反应物反应的动力学参数,并讨论了粒度对动力学参数的影响.结果表明,反应物粒度对该反应的速率常数、指前因子和表观活化能均有显著的影响;随着反应物粒径的减小,速率常数增大,指前因子和表观活化能减小,且指前因子的对数和表观活化能分别与反应物粒径的倒数呈线性关系.     

N-酰基取代苯并氮杂冠醚~1H和~(13)CNMR谱分析

冠醚化合物以其特殊的配合选择性受到化学工作者的重视,其结构与性能的研究已广泛引起人们的兴趣。本文对新合成的七种冠醚化合物测定了~1H和~(13)C NMR谱,并利用文献值和本组化合物的系列性对谱线进行了归属和讨论。实验部分七种冠醚化合物均由武汉大学化学系合成,其结构式见表1。样品在5mm样品管中以0.5ml CDCI_3(北京化工厂产品)为溶剂配成浓度约为0.5M的溶液。用美国Varian公司XL-200谱仪记谱。探头温度20.0±0.1℃,样品管旋转速度25±5Hz,以氘代氯仿为内锁场信号。     

Method of kinetic analysis of photodegradation: nifedipine in solutions

A rate equation for photodegradation was derived from Lambert-Beer's law and Grotthus-Draper's law: -dc/dt=k1(1-exp(-(k2c+k3(c0-c))))k2c/(k2c+k3(c0-c)) where c is the concentration of reactant, c0 is the initial concentration of reactant, t is time, k1 is the rate constant, and k2 and k3 are the absorption coefficient of reactant and its photodegradation product, respectively. In a case where the photodegradation products have no photoabsorption, k3 assumes the value of zero in the above general equation. In a case where the photodegradation products have the same spectrum and molar absorptivity as that of the reactant, k3 assumes the value of k2, and hence the photodegradation is not a first-order reaction; however, the equation itself gives the pseudo-first-order reaction rate equation. In a case where the concentration of reactant is high enough, the equation approaches a zero-order reaction rate equation. The photodegradation rate of nifedipine in solutions under a germicidal lamp, near an ultraviolet fluorescent lamp and a fluorescent lamp was analyzed using the above equation. The photodegradation rate was directly proportional to the amount of light absorbed, and fitted well with the equation. The above theoretical equation was substantiated by the photodegradation of nifedipine, and hence is expected to apply to other photosensitive drugs.     

High-temperature rate constant determination for the reaction of OH with iso-butanol

This work presents the first direct experimental study of the rate constant for the reaction of OH with iso-butanol (2-methyl-1-propanol) at temperatures from 907 to 1147 K at near-atmospheric pressures. OH time-histories were measured behind reflected shock waves using a narrow-linewidth laser absorption method during reactions of dilute mixtures of tert-butylhydroperoxide (as a fast source of OH) with iso-butanol in excess. The title reaction's overall rate constant (OH + iso-butanol →(k(overall)) all products) minus the rate constant for the β-radical-producing channel (OH + iso-butanol →(k(β)) 1-hydroxy-2-methyl-prop-2-yl radical + H(2)O) was determined from the pseudo-first-order rate of OH decay. A two-parameter Arrhenius fit of the experimentally determined rate constant in the current temperature range yields the expression (k(overall) - k(β)) = 1.84 × 10(-10) exp(-2350/T[K]) cm(3) molecule(-1) s(-1). A recommendation for the overall rate constant, including k(β), is made, and comparisons of the results to rate constant recommendations from the literature are discussed.     

Rate coefficients for the gas‐phase reaction of isoprene with NO3 and NO2

Rate coefficients for the gas‐phase reaction of isoprene with nitrate radicals and with nitrogen dioxide were determined. A Teflon collapsible chamber with solid phase micro extraction (SPME) for sampling and gas chromatography with flame ionization detection (GC/FID) and a glass reactor with long‐path FTIR spectroscopy were used to study the NO₃ radical reaction using the relative rate technique with trans‐2‐butene and 2‐buten‐1‐ol (crotyl alcohol) as reference compounds. The rate coefficients obtained are k(isoprene + NO₃) = (5.3 ± 0.2) × 10^?13 and k(isoprene + NO₃) = (7.3 ± 0.9) × 10^?13 for the reference compounds trans‐2‐butene and 2‐buten‐1‐ol, respectively. The NO₂ reaction was studied using the glass reactor and FTIR spectroscopy under pseudo‐first‐order reaction conditions with both isoprene and NO₂ in excess over the other reactant. The obtained rate coefficient was k(isoprene + NO₂) = (1.15 ± 0.08) × 10^?19. The apparent rate coefficient for the isoprene and NO₂ reaction in air when NO₂ decay was followed was (1.5 ± 0.2) × 10^?19. The discrepancy is explained by the fast formation of peroxy nitrates. Nitro‐ and nitrito‐substituted isoprene and isoprene‐peroxynitrate were tentatively identified products from this reaction. All experiments were conducted at room temperature and at atmospheric pressure in nitrogen or synthetic air. All rate coefficients are in units of cm³ molecule^?1 s^?1, and the errors are three standard deviations from a linear least square analyses of the experimental data. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 37: 57–65, 2005     

Molecular-dynamics simulations for nonclassical kinetics of diffusion-controlled bimolecular reactions

Molecular-dynamics simulations are presented for the diffusion-controlled bimolecular reaction A+B<==>C in two and three dimensions. The reactants and solvent molecules are modeled as spheres interacting via continuous potential-energy functions. The interaction potential between two reactants contains a deep well that results in a reaction. When the solvent concentration is low and the reactant dynamics is essentially ballistic, the system reaches equilibrium rapidly, and the reaction follows classical kinetics with exponential decay to the equilibrium. When the solvent concentration is high the particles enter the normal diffusion regime quickly and nonclassical behavior is observed, i.e., the reactant concentrations approach equilibrium as t(-d/2) where d is the dimensionality of space. When the reaction well depth is large, however, the reaction becomes irreversible within the simulation time. In this case the reactant concentrations decay as t(-d/4). Interestingly this behavior is also observed at intermediate times for reversible reactions.     

Kinetics of the chromium(III)/l‐glutamic acid complexation reaction: Formation,decay, and UV‐vis spectrum of a long‐lived intermediate

The kinetics of the aqueous reaction of Cr(III) with either l ‐glutamic acid or sodium hydrogen l ‐glutamate at pH 2.46‐5.87 have been followed by means of absorbance readings. The rate of formation of the reaction products showed acceleration‐deceleration periods, caused by the accumulation and posterior decay of an intermediate in nonnegligible concentration. A double‐exponential integrated rate law allowed obtaining two rate constants for each absorbance‐time experimental series, associated with the appearance (k₁) and decay (k₂) of the long‐lived intermediate. An increase of the initial concentrations of either hydrogen l ‐glutamate (apparent kinetic orders < 1) or hydroxide (kinetic orders = 1) ions resulted in an increase of both k₁ and k₂, but addition of an inert electrolyte (KNO₃) resulted in opposite effects on k₁ (decrease) and k₂ (increase). The experimental activation energies were 83 ± 10 (for k₁) and 95 ± 5 (for k₂) kJ mol⁻¹. The electronic spectrum of the low reactivity detected intermediate resembled more closely to that of the blue/green reactant than that of the violet reaction product. The low number of protons set free by the complexating hydrogen l ‐glutamate ligand seems to suggest that some polymerization of the coordinated amino acid (to form a di‐ or tripeptide) might take place. The available experimental data indicate that the coordination of the organic ligand must be preceded by the breakdown of a strong Cr(III)–H₂O chemical bond in the slow steps of the mechanism.     

Kinetics of Alkali-Catalyzed 2,5-Dimethylphenol-Forrnaldehyde Reaction

A kinetic study of the reaction between 2,5-dimethylphenol (2,5-DMP) and formaldehyde has been carried out at 65, 70, 75, and 80 ± 0.05° C by using sodium hydroxide as the catalyst. The solvent mixture used in the kinetic experiments was 50% (v/v) methanol-water. The various alkali concentrations used were 0.003, 0.006, 0.010, 0.018 and 0.025 N. The reaction was found to obey second-order rate law. The rate of reaction was observed to increase with an increase in the alkali concentration. The effect of changing the reactant concentrations and the nature of the solvent was also studied. The overall rate constant has been resolved into stepwise rate constants. The entropy of activation and Arrhenius parameters for the overall reaction have also been calculated.     

An ftir study of the reaction between nitrogen dioxide and alcohols

The reaction 2NO₂ + ROH = RONO + HNO₃ (R = CH₃ or C₂H₅) has been studied using the FTIR method at reactant pressures from 0.1 to 1.0 torr at 25°C. The termolecular rate constant for the forward reaction was determined to be (5.7 ± 0.6) × 10^?37 cm⁶/molec²·s for CH₃OH and (5.7 ± 0.8) × 10^?37 cm⁶/molec²·s for C₂H₅OH, that is, d[RONO]/dt = k[NO₂]²[ROH]. The corresponding equilibrium constants were measured as 1.36 ± 0.06 and 0.550 ± 0.025 torr^?1, respectively. These results are consistent with those of a previous study based on the NO₂ decay measurements at reactant pressures from 1 to 10 torr.     

Pressure dependence of secondary ion emission from selected transition metals under nitrogen dioxide

For Ar⁺ bombarded polycrystalline surfaces of Ta, Co, Ni, Pd and Pt the emission of positive secondary ions was observed using nitrogen dioxide as reactant gas with varied partial pressure (0.001 mPa <p _{spno}2 < 10 mPa) and dynamic SIMS conditions (2 keV; 32 A/cm²). The results indicate that NO₂ molecules appear to be completely destroyed in adsorption to Ta. Different behaviour was found for the other target metals. This can be explained by assuming surface species of partially molecular type. In some cases the results indicate two different modes of surface interaction with the reactant gas.     

循环流动固定床光催化反应器动力学数学模拟

以甲基橙为模型反应物,研究了连续循环固定床光催化反应器的动力学过程.根据光催化氧化过程特点,分析并建立了准一级反应动力学方程,对该反应系统的动力学过程进行动态数学模拟,用四阶Runge-Kutta法进行数值计算,结果表明数学模拟与实验数据相吻合.在该光催化反应体系中,处理量增加时实际反应速率常数k基本不变,而表观反应速率常数kapp变小,二者之间关系与反应器体积对处理量体积比（γ）密切相关;反应速率常数受起始浓度影响很大,在15～150 μmol•L－1浓度范围内,lnk=－0.48ln[c0]＋1.42;反应速率常数与光强的关系为k∝I0.5;反应速率常数受溶液pH值的影响也很大.     

Linear Chain Termination in the Kinetics of Postpolymerization of Dimethacrylates

The kinetics of postpolymerization (after turning off UV irradiation) of various dimethacrylates differing in their nature and molecular weight was studied over a wide range of temperatures. For each temperature, a series of kinetic curves, varying in the initial conversion during a dark period, was obtained. The proposed kinetic model is based on the following assumptions. The process in the interphase layer at the liquid monomer-solid polymer boundary has the most significant contribution to the kinetics of postpolymerization. Chain termination in the interphase layer occurs by the unimolecular reaction, is controlled by the chain growth rate, and presents the act of self-burying of an active radical in a conformational trap. A wide spectrum of characteristic times is inherent in unimolecular chain termination, and the relaxation function is described by the Kohlraush' stretched exponential law. The rate law obtained agrees well with experimental data. This fact made it possible to estimate the rate constants (k _t) and the activation energies of chain termination and to establish the scale dependence of k _t on the molar concentration [M₀] of the monomer in a block. It is suggested that both the stretched exponential law and the scale k _t-[M₀] dependence are due to a wide spectrum of characteristic times of relaxation exhibiting the properties of a fractal set.