对硅酸聚合机制反应级数的验证

用胶凝法研究酸化了的不同摩尔比 (Si O2 /Na2 O)的硅酸钠溶液的胶凝速度 ,发现在恒盐条件下 ,硅酸胶凝速度常数是 2 ,这个结果和我们过去所提出的硅酸聚合机制符合一致。     

臭氧与二乙胺和三乙胺气相反应的速率常数

利用自制的烟雾箱系统研究了臭氧与二乙胺和三乙胺的气相反应动力学. 实验过程中保证二乙胺和三乙胺浓度远远大于臭氧浓度, 使得实验在准一级条件下进行. 加入环己烷以消除实验过程中可能产生的OH自由基对反应的影响. 在(298±1) K和1.01×105 Pa条件下, 测得臭氧与二乙胺和三乙胺反应的绝对速率常数值分别为(1.33±0.15)×10^-17和(8.20±1.01)×10^-17 cm³·molecule^-1·s^-1. 与文献中已有的其它胺类的臭氧反应数据比较后发现, 臭氧与胺的反应可以用亲电反应机制来解释. 另外, 通过对比发现, 臭氧与三取代的烷基胺类的反应速率要远远大于其与二取代的烷基胺类的反应速率. 这在一定程度上可有助于解释外场观测到的气溶胶相中二烷基胺盐较多的事实. 利用测得的速率常数和大气中臭氧浓度, 还估算了二乙胺和三乙胺与臭氧反应的大气寿命. 结果显示, 与臭氧的反应是二乙胺和三乙胺在大气中的一种重要的消除途径, 尤其是在污染严重地区.     

Kinetics of radical telomerization of vinylidene fluoride in the presence of CCl3Z chain transfer agents

The kinetics of radical telomerization of VDF at 141 °C, initiated by ditertbutylperoxide, in the presence of three chain transfer agents (CTAs), HCCl₃, CCl₄ and CCl₃Br, are presented. The values of the chain transfer constants were assessed as 35, 0.25 and 0.06 at 141 °C for CCl₃Br, CCl₄ and HCCl₃, respectively. The values of the degree of polymerization (DP_n) were obtained for each CTA and were compared for the same CTA concentration. Hence, CCl₃Br behaved as an efficient CTA towards VDF and usually afforded the monoadduct selectively, but in certain conditions the VDF diadduct can also be produced. In contrast, HCCl₃ was not so efficient since a polymeric structure was identified as the major product.     

氢键缔合体的分子力场和振动光谱的研究

氢键缔合体的分子力场和振动光谱的研究孙泽民，王丰，唐作华，鄢国森（四川大学化学系，成都，６１００６４）关键词氢键，力常数，振动频率氢键缔合体的结构在一定程度上受单体间氢键作用的影响，而振动光谱对分子结构及其坏境的变化极为敏感，故其在探讨分子间氢键方面...     

Determination of the surface tension of surfactant solutions applying the method of Lecomte du Noüy (ring tensiometer)

Summary Starting from a comparative assessment of the outstanding works on the ring method (du Noüy) for the determination of the surface tension of liquids and its solutions it is shown that the application of this method to surfactant solutions can lead to substantial errors if one follows conventional conditions. These errors are mainly connected with so far unknown phenomena occurring during the raising of the ring and concerning the influence of the hydrophilic vessel wall above the solution level and the stretching of the solution surface. This is demonstrated quantitatively with surfactant solutions of different kind and concentration. These effects can be explained theoretically very simply by introducing certain assumptions on the behaviour of a surfactant adsorption layer on the inner vessel wall. Conditions leading to the elimination of these errors are given, thus enabling the application of the ring method to the determination of the surface tension of surfactant solutions.With 10 figures and 3 tables     

The influence of the mercury and thallium atoms in organomercury and organothallium nitroxyl radicals on their reactivity

An increase is found in the reactivity of organomercury and organothallium nitroxyl mono- and biradicals of the imidazoline type in comparison with the analogous compounds without organometallic fragments. This is explained by the formation of coordination bonds NHg, NTl, and NOHg.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 224–226, January, 1993.     

Monolayer films of PS-b-PEO diblock copolymers at the air/water- and an oil/water-interface

 Amphiphilic diblock copolymers consisting of a hydrophobic polystyrene block (PS) and a hydrophilic poly(ethylene oxide) block (PEO) with block sizes of 1000 or 3000 g/mol for both blocks were studied at the air/water and toluene/water interface. Measurements of the film pressure π of spread monolayers at the water surface reveal two limiting regimes of the π−a _m isotherms, in which the mean molecular area a _m is determined either by the size of the hydrophilic or the hydrophobic blocks of the PS-PEO molecules. The interfacial activity of the block copolymers at the toluene/water interface was studied by measuring the interfacial tension σ over a wide range of concentrations. Pronounced differences in the temperature dependence of the interfacial tension were observed, depending mostly on the block length of the hydrophilic PEO block. From the temperature dependence of σ it is inferred that for the block copolymers with the PEO block size of 3000 g/mol the phase inversion temperature (PIT) is well above 60 °C while for those with a PEO block size of 1000 g/mol the PIT is below or near 25 °C in the toluene/water system. Received: 5 February 1998 Accepted: 16 February 1998     

Studies on the Complexes of N,N′-Bis[o-(diphenylphosphino)benzylidene]ethylenediamine with Transition Metal Ions

The thermodynamic parameters for the interaction of Cu²⁺, Ni²⁺, Co²⁺, Cd²⁺, andAg⁺ with the new title ligand have been determined by titration calorimetry in 50% THF–methanol (V/V) at 25 °C.Ag⁺ exhibited remarkably higher complexation selectivity.Ag⁺ and several transition metal ions have been transportedusing this ligand as carrier in a bulk liquid membrane. CompetitiveAg⁺–M²⁺ transport studies have also beencarried out for the same system. In this membrane transport study, high transport of Ag⁺ was observed in both single and competitiveAg⁺–M²⁺ transport studies. The complexformation of N,N-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (P₂N₂) with silver,[Ag(P₂N₂)] (NO₃), (1) is reported. Complex 1 has been characterized by X-ray crystallography. 1 ismonoclinic, space group P2_1/n (No. 14), with cell dimensionsa = 13.398(4) , b=12.577(5) , c = 21.521(4) , =100.14(2) , V = 3570(2) ³ and Z = 4.     

C2H4-K体系中振动态至电子态传能的研究

用TEA CO_2激光将C_2H_4分子激发到高振动激发态，高振动激发态的C_2H_4分子与基态的K原子碰撞发生振动态→电子态（V→E）传能过程，根据提出的能级组模型，对测得的时间分辨原子荧光信号进行处理，获得温度在453－663 K范围内，C_2H_4-K体系中V→E传能速率的数量级为10~(-10)/cm~3·molecule~(－1)·s~(－1)，对应的碰撞传能截面约为0.30～0.80 nm．随着反应温度升高，V→E传能截面减小．上述实验结果表明碰撞体间吸引相互作用在这种非共振的V→E传能过程中起主要作用．利用多极相互作用势下的碰撞络合物模型对实验结果进行了讨论．     

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.