Theoretical study and rate constant calculation for the reactions of SH (SD) with Cl2, Br2, and BrCl

The mechanisms of the SH (SD) radicals with Cl2 (R1), Br2 (R2), and BrCl (R3) are investigated theoretically, and the rate constants are calculated using a dual-level direct dynamics method. The optimized geometries and frequencies of the stationary points are calculated at the MP2/6-311G(d,p) and MPW1K/6-311G(d,p) levels. Higher-level energies are obtained at the approximate QCISD(T)/6-311++G(3df, 2pd) level using the MP2 geometries as well as by the multicoefficient correlation method based on QCISD (MC-QCISD) using the MPW1K geometries. Complexes with energies less than those of the reactants or products are located at the entrance or the exit channels of these reactions, which indicate that the reactions may proceed via an indirect mechanism. The enthalpies of formation for the species XSH/XSD (X = Cl and Br) are evaluated using hydrogenation working reactions method. By canonical variational transition-state theory (CVT), the rate constants of SH and SD radicals with Cl2, Br2, and BrCl are calculated over a wide temperature range of 200-2000 K at the a-QCISD(T)/6-311++G(3df, 2pd)//MP2/6-311G(d, p) level. Good agreement between the calculated and experimental rate constants is obtained in the measured temperature range. Our calculations show that for SH (SD) + BrCl reaction bromine abstraction (R3a or R3a') leading to the formation of BrSH (BrSD) + Cl in a barrierless process dominants the reaction with the branching ratios for channels 3a and 3a' of 99% at 298 K, which is quite different from the experimental result of k3a'/k3' = 54 +/- 10%. Negative activation energies are found at the higher level for the SH + Br2 and SH + BrCl (Br-abstraction) reactions; as a result, the rate constants show a slightly negative temperature dependence, which is consistent with the determination in the literature. The kinetic isotope effects for the three reactions are "inverse". The values of kH/kD are 0.88, 0.91, and 0.69 at room temperature, respectively, and they increase as the temperature increases.     

2-(8-羟基喹啉-5-磺酸-7-偶氮)-1,8-二羟基-3,6-萘二磺酸与牛血清白蛋白的相互作用

用平衡透析法和分光光度法研究了 2 (8 羟基喹啉 5 磺酸 7 偶氮 ) 1,8 二羟基 3,6 萘二磺酸与牛血清白蛋白 (BSA)在酸性溶液中的结合反应 ,认为 8Q5SAC与BSA之间的结合力是以静电引力为主的非共键作用力 ,并探讨了其结合模型。在 2 98K下 ,测得这一反应的最大结合数为 35～ 40 ,结合常数为 6 .1× 10 5L mol。还研究了溶液基本条件如酸度和离子强度等对 8Q5SAC与牛血清白蛋白分子复合物形成的影响 ,在pH =3.34条件下 ,标准工作曲线的线性范围为 0 .2 0～ 46 .90mg L。     

1,2-聚丁二烯介电松弛的复平面分析

本文对1,2-聚丁二烯的介电松弛进行了复平面分析.结果表明,在1,2-聚丁二烯的玻璃化转变过程中,ε″(ω)与ε＇(ω)的关系满足Havriliak-Negami方程.由复平面图求出了样品的静态和光频下的介电系数,平均松弛时间和松弛时间分布参数.利用所得数据讨论了1,2-聚丁二烯在玻璃化转变过程中的构象变化、松弛时间分布和平均偶极矩等问题.     

Gas–liquid partition coefficients and Henry's law constants of methyl mercaptan in aqueous solutions of Fe(II)–CDTA chelate complex

Utilization of ferric chelate complex of trans-1,2-cyclohexanediaminetetraacetic acid (CDTA) for the oxidative scrubbing of H₂S and CH₃SH in Kraft mill streams can be beneficial from the standpoints of iron protection against precipitation and oxygen-mediated regenerative oxidation of the ferrous chelate CDTA. The physical solubility of methyl mercaptan in CDTA–Fe(III) complex cannot be measured directly because of oxidation of the sulfur-bearing gaseous species with the ferric chelate. Therefore, this investigation was carried out to determine the gas–liquid partition coefficients and Henry's law constants of methyl mercaptan in aqueous iron-free CDTA solutions and non-reacting ferrous chelate solutions (CDTA–Fe(II) complex), using the static headspace method with an estimated accuracy of about 2%. Experiments with aqueous solutions of chelate concentrations varying between 38 and 300 mol m⁻³ were carried out at temperatures between 298 and 333 K and atmospheric pressure. It was shown that the methyl mercaptan solubility decreases with increasing temperature for all systems but was not much influenced, in the studied conditions, by the chelate concentration especially at larger temperatures.     

Effect of cooperativity on the O-H stretching force constant in associated water species

CNDO/force calculations have been employed to calculate the O-H stretching force constants for various structures of associated water species such as water-dimethylether, water-acetonitrile, water-lithium fluoride, linear and cyclic water polymers. The variation in the O-H stretching force constant in A_m… O-H… D_n species where A_m and D_n represent, respectively,m number of electron-acceptor andn number of electron-donor molecules, is explained on the basis of the cooperativity effect. With increasing electron-acceptor power of A and electron-donor power of D, the hydrogen-bonded O-H stretching force constant is significantly reduced. The results obtained in these studies are in general agreement with experimental observations reported earlier.     

恒电流库仑法测定基准试剂三氧化二砷的含量

用恒电流库仑法测定基准试剂三氧化二砷的含量，以恒电流通过含有碘化钾，基准试剂三氧化二砷试样的弱碱性水溶液，利用工作电极铂阳极上电生滴定剂I2与亚砷酸盐定量反应，以死停终点法确定滴定终点，测量出电解电流和电解时间，根据法拉第电解定律并利用EXCEL计算出基准试剂三氧化二砷的含量。方法的回收率为100％。     

Concentrated electrolyte solutions at high temperatures and pressures

A survey is given of recent experimental results obtained from high-temperature, high-pressure investigations with water, aqueous solutions, and ionic fluids. Data on the static dielectric constant of water to 550°C and 5 kbar are given and discussed with respect to their relation to water structure. Infrared and Raman spectra of HDO in pure water have been obtained to 400°C and 4 kbar, which give information on hydrogen bonding. Xe–H₂O and CO₂–H₂O mixtures were investigated in the infrared. Ni(II) and Cu(II) complexes were investigated by absorption spectroscopy in aqueous solutions of high chloride content to 350°C and 2–6 kbar. The gas-liquid critical point of ammonium chloride was found at 880°C and 1635 bars. This fluid appears to be predominantly ionic even in the critical region. The possibility of converting pure polar fluids such as ammonia and water into concentrated ionic solutions by self-ionization at very high pressures is mentioned.This paper was presented at the symposium, The Physical Chemistry of Aqueous Systems, held at the University of Pittsburgh, Pittsburgh, Pennsylvania, June 12–14, 1972, in honor of the 70th birthday of Professor H. S. Frank.     

Solvent extraction of sodium picrate with 15-crown-5 into carbon tetrachloride. The determination of the dimer-formation constant of a crown ether-univalent metal salt 1∶1∶1 complex

The theory is derived to determine the dimer-formation constant,K ₂, of a crown ethermetal salt 111 complex in organic solvents of low dielectric constant by solvent extraction. The theoretical predictions are verified experimentally by extraction of sodium picrate (NaA) with 15-crown-5 (15C5) into carbon tetrachloride. All the experiments were conducted at 25°C. The logK ₂ value of the Na(15C5)A complex in carbon tetrachloride has been determined to be 4.05±0.11. Moreover, the partition constant of the complex is calculated.     

Dielectric relaxation of poly(ester-ether-carbonate) multiblock terpolymers

The dielectric properties of a series of poly(ester-ether-carbonate) multiblock terpolymers have been investigated as a function of ether and carbonate composition in the frequency range of 10³–10⁶ Hz. The degree of polymerization of the samples was determined by viscosimetry measurements. The weight fraction, degree of crystallinity, and melting temperatures were characterized by means of x-ray diffraction and DSC methods. Dielectric behavior has been discussed in terms of Havriliak-Negami formulation. The variation of the dielectric properties with temperature has been associated with two relaxation processes: a) the -relaxation process observed at low temperature, which is associated to local motion of polar groups attached to both the soft and the hard segments, and b) the process assigned to long-range molecular motions above the glass transition temperature.     

邻-甲氧基苯酚和α-,β-环糊精包合现象的理论与实验研究

通过紫外可见光谱法考察了水溶液中邻-甲氧基苯酚(o-Mop)和α-与β-环糊精(CD)的分子间相互作用, 利用Hildebrand-Benesi方程给出了两个包合物的稳定常数(K_s). 采用半经验PM3方法研究了α-,β-CD和o-Mop及其类似物苯酚(Phe)、丁香酚(Eug)之间的包络作用, 阐述了这些主客体包合作用过程中体系能量随主客体相对位置改变而变化的细节, 据此推断出主-客体包合物可能的分子结构, 计算了包合物的稳定化能(ΔE_s). 研究结果表明, 本文所选主客体体系而言, 当客体和同一种主体分子作用时, 超分子包合物的ΔE_s随着客体分子苯环上取代基团数目的增多而增加. 基于PM3方法优化得到的主-客体包合物在真空中的分子结构和通过实验方法在水溶液中测定的结构一致.