正丁基锂四氢呋喃引发α-甲基苯乙烯阴离子平衡聚合动力学及反应机理研究

本文研究了以正丁基锂为引发剂,四氢呋喃为添加剂,环己烷为溶剂中的α-甲基苯乙烯阴离子平衡聚合动力学。讨论了体系中的反应活性种;提出了聚合机理;得到了聚合温度为20℃时的平衡单体浓度与活性种速率常数及添加剂浓度之间的关系式。     

Thermodynamic and Equilibrium Composition of Using Iron Oxide as an Oxygen Carrier Nonflame Combustion Technology Analysis in

本文介绍了一种新的燃烧体系--熔融盐循环热载体无烟燃烧技术。这种燃烧体系杜绝环境污染气体NOx和CO2的排放，可以实现真正零排放的目标。计算了以Fe2O3作为氧载体的无烟燃烧体系的热力学参数。用最小吉布斯自由能原则，分析了Fe2O3与CH4的平衡组成。分析表明，如果要想在产物中产生高纯度的CH4完全氧化产物CO2和H2O，Fe2O3与CH4必须达到高摩尔比，如果Fe2O3的量不足，就会产生较多的部分氧化产物如CO，H2甚至C     

等规聚苯乙烯的分子量分级

用配位聚合法得到的高等规度的等规聚苯乙烯(i-PS),一般具有较宽的分子量分布,对其进行分子量分级是比较难的,迄今已有不少这方面的报道,其中包括采用热力学的方法,以及采用分子量降解的方法。为了获得分子量分布较窄的i-PS样品来研究单链单晶,我们也进行了i-PS的分级研究,我们选用了一种新的溶剂/不良溶剂体系对i-PS     

The Equilibrium Structure of Methyl Fluoride

The equilibrium structure of CH₃F has been determined using new sets of accurate rotational constants that have been determined by taking into account all the interactions between the excited vibrational states. This experimental structure is in excellent agreement with the equilibrium geometry calculated at the CCSD(T) level of theory with the cc-pV(5, Q)Z basis set (including corrections for the core correlation and for the effect of diffuse functions on fluorine). Finally, the experimental and ab initio structures have been combined by a least-squares analysis. The results are , and L _e(HCH) = 110.2 (1)°, where the uncertainties shown in parentheses correspond to three standard deviations.     

Solid-state reactions of organometallic aldehydes with optically active primary β-hydroxyamines

The solid-state reactions of crystalline ferrocenyl- and ruthenocenylaldehydes with optically active primary β-hydroxyamines were studied at ∼20 °C. The yield of the products increases substantially in the presence of K₂CO₃. The tautomeric equilibrium between imines and diastereomeric oxazolidines with the predominant formation of one of them is established in solutions of the products in CDCl₃. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2240–2243, December, 1997.     

双冠醚研究(Ⅳ)——Schiff碱型和仲胺型双-(苯并15冠-5)对碱金属苦味酸盐的萃取行为

仲胺型双冠醚与四苯硼酸碱金属盐在丙酮溶液中。25℃下的电导说明它们与Na~+可能形成1∶1络合物(冠醚单元∶金属离子),而与K~+、Rb~+、Cs~+离子则形成2∶1络合物。用Schlff碱型和仲胺型双-(苯并15-冠-5)在水-氯仿体系中进行萃取,测量了分配比D和萃取平衡常数K,发现后者的K值均大于前者。双冠醚F_2对K~+的萃取能力最强,选择性最佳。     

Computer modelling of the conformational equilibrium of 2-and 2,5,5-substituted 1,3,2-dioxaborinanes

Empirical, semiempirical, and nonempirical quantum-chemical methods were used to study the conformational equilibrium of 2,5,5-substituted 1,3,2-dioxaborinanes. The sofa invertomers were found to correspond to the local and global minima on the potential energy surface. The position of the equilibrium between these forms is a function of the substituents at C₍₅₎ of the heterocycle. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1860–1865, December, 2007.     

Sorption of alkali metals and silver nitrates from binary and multicomponent solutions by a crown-containing polymer

The equilibrium in the systems containing a polymer based on dibenzo-18-crown-6 and binary or multicomponent aqueous solutions of NaNO₃, KNO₃, RbNO₃, and AgNO₃ was studied. The constants of the sorption of the individual electrolytes from solution into the polymer were determined. Preliminary calculations of the phase composition on sorption of 11 mixtures of electrolytes with a common anion from the data on the equilibria in the systems with one electrolyte are possible.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 464–466, March, 1993.     

Characterization of the solid phases of paracetamol and fenamates at equilibrium in saturated solutions

Differential scanning calorimetry (DSC), supported by hot stage microscopy, IR spectroscopy and X-ray powder diffractometry, was used to investigate the characteristics of the solid phases of mefenamic, niflumic, and flufenamic acids and of paracetamol, before and after equilibration with saturated solutions in different solvents. Mixtures of Lewis base (dioxane and ethyl acetate) and amphiprotic solvents (ethanol and water) were prepared for evaluating the influence of both nature and polarity of the solvents. Solid-state analysis performed on the original samples (commercial products) made it possible to establish that paracetamol, mefenamic acid and flufenamic acid were in their respective Form I. No polymorphic modifications are known for niflumic acid. Paracetamol, niflumic and mefenamic acids did not show any change after equilibration with the various solvents or solvent mixtures, regardless of their different chemical nature. In contrast, DSC, IR and X-ray analyses revealed the partial recrystallization of flufenamic acid into its polymorphic Form III in solid phases at equilibrium with ethanol, ethyl acetate and their blends, as well as in dioxane-water mixtures containing 30 to 100% dioxane and in ethanol-water mixtures with a water content less than 50%. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of group II metal cations on catecholate oxidation.

The unexpected effects of Ca(2+) on the free-radical chain reactions of dopamine, norepinephrine, isoproterenol, and pyrocatechol oxidation are studied using oxygen consumption measurements, EPR-spectroscopy, UV/VIS spectrophotometry, and by potentiometric titration. It is found that the formation of Ca(2+)-catecholate complexes is accompanied by an increase in the dissociation constants (K(ai) ) of their phenolic hydroxyls. At pH>pK(ai) and in the presence of alkaline-earth metal cations, the rate of catecholate oxidation increases (Ca(2+), Mg(2+)> Sr(2+), Ba(2+)), whereas on addition of Zn ions the rate decreases. The effects of Group II metal cations on catecholate autoxidation are concomitant with a transient increase of the EPR signal for metal-semiquinonate complexes. Therefore, the effects of Ca(2+) and other alkaline-earth metal cations on catecholate autoxidation can be defined as 1) additional deprotonation of catechol OH-groups involved in the formation of M(2+)-catecholate complexes, the latter exceeding catechols in the susceptibility to dioxygen-induced oxidation and 2) formation of relatively stable free-radical intermediates responsible for chain propagation.