电子转移反应O2+O2·-→O2·-+O2的从头算研究

利用abinitio方法,在UHF,UMP2及不同基组3-21G,6-31G^*,6-311+G^*和UMP2(full)/6-311+G^*水平上,研究了O~2/O~2^.^-自交换电子转移反应。优化了电子转移前后反应物和产物的结构,研究了体系能量的变化,计算了自交换电子转移反应的内重组能。对UHF方法和UMP2方法的计算结果进行了比较,并与实验结果进行了对照。结果表明UHF方法由于没有考虑组态相互作用,计算结果存在较大偏差,UMP2(full)/6-311+G^*水平上的计算结果与实验值吻合较好。在UMP2(full)/6-311+G^*水平上计算了气相自交换电子转移反应速率常数。在优化了电子转移复合物结构的基础上考虑了溶剂效应的影响,计算了水溶液中的溶剂重组能。研究结果表明O~2/O~2^.^-体系电子转移反应的活化能主要来源于溶剂重组能的贡献。最后计算了该反应在水溶液中的反应速率常数。理论计算结果与实验值吻合得很好。     

Synthesis and thermochemical characteristics of Na2O · Al2O3 · 2.5H2O

A pure phase of monosodium aluminate hydrate Na₂O · Al₂O₃ · 2.5H₂O (MAH) is synthesized and characterized by means of XRD, IR, SEM, TGA, and DSC. The heat capacity of the compound is measured in the temperature range of ?100 to 100°C, and the thermal contributions to enthalpy and entropy are calculated. The standard entropy, enthalpy, and Gibbs energy of formation of MAH at 298 K are estimated.     

Die Verbindungen 2SiO2·P2O5 und 2GeO2·P2O5

Zusammenfassung Bei röntgenographischen Untersuchungen im System GeO₂-P₂O₅ wird eine Verbindung der Zusammensetzung 2 GeO₂·P₂O₅ aufgefunden. Einkristallaufnahmen ergeben eine hexagonale (trigonale) Elementarzelle mita=7,99₈ undc=24,8₆ Å. Die schon beschriebene Verbindung 2 SiO₂·P₂O₅ erweist sich als isotyp:a=7,86₂ undc=24,1₃ Å.     

2MgO·2B2O3·MgCl2·14H2O-MgCl2-H2O体系30℃相平衡

用相平衡方法研究2MgO@2B2O3@MgCl2@14H2O在30℃不同质量分数MgCl2水溶液中的溶解转化产物及其溶解度.结果表明,该复盐在MgCl2的质量分数0～2%浓度范围,发生不同步溶解并转化为多水硼镁石(2MgO@3B2O3@15H2O);在MgCl2的质量分数2%～13.8%浓度范围,转化为柱硼镁石(MgO@B2O3@3H2O),这一结果比文献报导的该硼酸盐的形成温度低了13℃,为盐湖硼酸镁矿物柱硼镁石形成的解释提供了物理化学依据;而在MgCl2质量分数大于13.8%时,同步溶解,不发生转化.提出了溶解相转化反应机理.     

209Bi NQR in Mixed Oxides 2Bi2O3· B2O3, 3Bi2O3· 5B2O3, and Bi2O3· 3B2O3

It was earlier found from nuclear quadrupole resonance (NQR) measurements and computer modeling that -Bi₂O₃, Bi₃O₄Br and mixed oxides Bi₂O₃· 2Al₂O₃, Bi₂O₃· 2Ga₂O₃, Bi₂O₃· 3GeO₂, and 2Bi₂O₃· 3GeO₂exhibit local ordered magnetic fields from 30 to 200 G. It thus follows that these compounds are not diamagnets in a conventional sence of the word. With the aim of revealing previously unknown magnetic properties in bismuth(III) oxide-based Main Group element compounds, the mixed bismuth–boron oxides 2Bi₂O₃· B₂O₃, 3Bi₂O₃· 5B₂O₃, and Bi₂O₃· 3B₂O₃were prepared and studied using ²⁰⁹Bi NQR. The quadrupole interactions of the ²⁰⁹Bi nuclei and their electronic environment were studied, the crystallochemical features of the compounds were discussed, and the conformity of the ²⁰⁹Bi results to the X-ray structure data was verified. The preliminary tests in the field of a permanent magnet showed that the resonance intensities increase in external magnetic fields, indicating that a magnetism of unknown nature develops in the titled compounds. It was found reasonable to continue studies of the magnetic properties of these compounds using single-crystal ²⁰⁹Bi NQR in external magnetic fields.     

Phase diagram and IR spectral investigations of the 2TeO2 · V2O5Li2O · V2O5 · 2TeO2 system

By means of X-ray phase analysis, IR spectroscopy, and DTA, the system 2TeO₂ · V₂O₅Li₂O · V₂O₅ · 2TeO₂ was investigated and its phase diagram was constructed. The formation of a new compound with composition Li₂O · 3V₂O₅ · 6TeO₂, melting incongruently was documented. A comparison of the bands in the IR spectrum was made. Stable glasses in the whole range of concentrations were prepared. From the IR spectra of the glasses, the corresponding crystallization products, and the data of known crystal structures, a model of the short-range order in the glasses was proposed.     

Parameters of Li2O2 · H2O crystallization from the LiOH-H2O2-H2O ternary system

The decomposition kinetics of peroxide products contained in the liquid phase of the LiOH-H₂O₂-H₂O ternary system were studied, and the applicability of the solubility method to studying this system was demonstrated for hydrogen peroxide concentrations in the liquid phase from 2 to 6 wt % and temperatures of 21–33°C. The stabilizing influence of solid Li₂O₂ · H₂O on hydrogen peroxide decomposition was demonstrated. The temperature and concentration boundaries of existence were determined for the Li₂O₂ · H₂O phase, whose identity was verified by chemical analysis and qualitative X-ray powder diffraction analysis.     

Heat capacity and thermodynamic functions of MnCl2·2H2O and MnCl2·2D2O

The heat capacities of MnCl₂·2H₂O and MnCl₂·2D₂O have been experimentally determined from 1.4 to 300 K. The smooth heat capacity and the thermodynamic functions (H°_T − H°₀) and S°_T are reported for the two compounds over the 10 and 300 K temperature range. The error in the thermodynamic functions at 10 K is estimated at 3%. Additional error in the tabulated values arising from the heat capacity data above 10 K is thought to be less than 1%. Lambda-shaped heat capacity features associated with antiferromagnetic ordering were observed at 6.67 ± 0.08 and 6.61 ± 0.08 K for the dihydrate and dideuterate, respectively. In addition, compound heat capacity anomalies consisting of a small lambda-shaped feature at 57.7 ± 0.5 K with a comparably large high-temperature shoulder extending to approximately 70 K were observed in both the dihydrate and dideuterate. The entropies associated with these anomalies are 0.42 ± 0.04 and 1.04 ± 0.04 J/mole-K, respectively.     

Thermodynamic properties of two zinc borates: 3ZnO·3B2O3·3.5H2O and 6ZnO·5B2O3·3H2O

Two pure zinc borates with microporous structure 3ZnO·3B₂O₃·3.5H₂O and 6ZnO·5B₂O₃·3H₂O have been synthesized and characterized by XRD, FT-IR, TG techniques and chemical analysis. The molar enthalpies of solution of 3ZnO·3B₂O₃·3.5H₂O(s) and 6ZnO·5B₂O₃·3H₂O(s) in 1 mol · dm⁻³ HCl(aq) were measured by microcalorimeter at T = 298.15 K, respectively. The molar enthalpies of solution of ZnO(s) in the mixture solvent of 2.00 cm³ of 1 mol · dm⁻³ HCl(aq) in which 5.30 mg of H₃BO₃ were added were also measured. With the incorporation of the previously determined enthalpy of solution of H₃BO₃(s) in 1 mol · dm⁻³ HCl(aq), together with the use of the standard molar enthalpies of formation for ZnO(s), H₃BO₃(s), and H₂O(l), the standard molar enthalpies of formation of −(6115.3 ± 5.0) kJ · mol⁻¹ for 3ZnO·3B₂O₃·3.5H₂O and −(9606.6 ± 8.5) kJ · mol⁻¹ for 6ZnO·5B₂O₃·3H₂O at T = 298.15 K were obtained on the basis of the appropriate thermochemical cycles.     

The double-layered hydro­xide 3CaO·Al2O3·0.5CaBr2·0.5CaCl2·10H2O

The title compound, calcium oxide–dialuminium trioxide–calcium dibromide–calcium dichloride hydrate (3/1/0.5/0.5/10), also formulated as Ca₂Al(OH)₆Br_0.478Cl_0.522·2H₂O (dicalcium aluminium hydro­xide hemibromide hemichloride dihydrate), is a double-layered hydro­xide which belongs to the solid solution Ca₂Al(OH)₆Br_xCl_1−x·2H₂O, where x can vary from 0 to 1. Chloride and bromide anions of the negatively charged interlayer [Br_0.5Cl_0.5·2H₂O]⁻ share statistically the same crystallographic site. Al³⁺ and Ca²⁺ cations are coordinated by six and seven O atoms, respectively. All water mol­ecules are bonded to Ca²⁺ cations and assume the seventh coordination position. Anions in the interlayer are surrounded by ten H atoms. Br⁻ and Cl⁻ are therefore connected to the main layer by ten hydrogen bonds, six of 2.74 (2) Å and four of 2.52 (5) Å, where the donors are hydroxyl groups and water mol­ecules, respectively. Like the chloride equivalent, the title compound is a 6R polytype with trigonal space group Rc and lattice parameters a = 5.7537 (4) Å and c = 48.108 (4) Å.     

2MgO·2B2O3·MgCl2·14H2O-H2O体系在沸点温度的相转化研究

2MgO·2B2O3·MgCl2·14H2O(氯柱硼镁石)是从天然浓缩盐卤中得到的一种新硼酸镁盐[1].已报道过在实验室中模拟合成盐卤对该复盐的合成条件[2].为了探讨该复盐在盐湖沉积过程中的形成和转化条件,对其在10～60℃水中溶解及相转化动力学过程做过研究,其中10～50℃时的最终溶解转化产物是2MgO·3B2O3·15H2O(多水硼镁石)[3],60℃是MgO.B2O3.H2O(柱硼镁石)[4].     

ZnSO4·CO(NH2)2·2H2O和MgCl2·NH4Cl·6H2O的热分解动力学研究

采用TG-DSC研究了ZnSO4·CO(NH2)2·2H2O和MgCl2·NH4Cl·6H2O的热分解反应,并对其中的脱水过程及部分分解过程进行了动力学计算,由Fridman、Ozawa-Flynn-Wall、ASTME698三种方法得出峰温时的活化能值与指前因子值,通过优化选择出了热分解过程最佳机理函数.     

Theoretical Study of the Dehydration Process of MgCl_2·4H_2O to MgCl_2·2H_2O

Density functional theory was employed to study the dehydration mechanism of MgCI_2·4H_2O. Analysis of potential energy surface(PES) of possible pathways indicated that the most possible way was one of the water molecules halfly dissociated with an elongated bond distance with Mg~(2+),where electrostatic interaction played a leading role; another water molecule dissociated sequentially. It was in agreement with the result from differencial thermal analysis. The dehydration process of MgCI_2·4H_2O was clarified theoretically,promoting the theoretical study of dehydration of MgCI_2·2H_2O.     

Magnetic and optical investigation of 40SiO2·30Na2O·1Al2O3·(29 − x)B2O3·xFe2O3 glass matrix

Samples of 40SiO₂·30Na₂O·1Al₂O₃·(29 − x)B₂O₃·xFe₂O₃ (mol%), with 0.0 ≤ x ≤ 17.5, were prepared by the fusion method and investigated by electron paramagnetic resonance (EPR), optical absorption (OA) and Mössbauer spectroscopy (MS). The EPR spectra of the as-synthesized samples exhibit two well-defined EPR signals around g = 4.27 and g = 2.01 and a visible EPR shoulder around g = 6.4, assigned to isolated Fe³⁺ ion complexes (g = 4.27 and g = 6.4) and Fe³⁺-based clusters (g = 2.01). Analyses of both EPR line intensity and line width support the model picture of Fe³⁺-based clusters built in from two sources of isolated ions, namely Fe²⁺ and Fe³⁺; the ferrous ion being used to build in iron-based clusters at lower x-content (below about x = 2.5%) whereas the ferric ion is used to build in iron-based clusters at higher x-content (above about x = 2.5%). The presence of Fe²⁺ ions incorporated within the glass template is supported by OA data with a strong band around 1100 nm due to the spin-allowed ⁵E_g–⁵T_2g transition in an octahedral coordination with oxygen. Additionally, Mössbauer data (isomer shift and quadrupole splitting) confirm incorporation of both Fe²⁺ and Fe³⁺ ions within the template, more likely in tetrahedral-like environments. We hypothesize that ferrous ions are incorporated within the glass template as FeO₄ complex resulting from replacing silicon in non-bridging oxygen (SiO₃O⁻) sites whereas ferric ions are incorporated as FeO₄ complex resulting from replacing silicon in bridging-like oxygen silicate groups (SiO₄).     

Al2O3·3H2O阻燃环氧树脂机理探讨

采用氧指数测定法与热重法研究了Al2O3·3H2O对环氧树脂固化物的阻燃效果与机理.结果表明,Al2O3·3H2O在热分解方面与树脂固化物有阻燃匹配性,并能以零级反应快速失去2个结晶水分子,失水后形成的活性氧化铝促进了树脂固化物热解时转化成难燃物的能力,具有较高的阻燃效果.     

Thermochemistry of two lead borates; Pb(BO2)2·H2O and PbB4O7·4H2O

Two pure hydrated lead borates, Pb(BO₂)₂·H₂O and PbB₄O₇·4H₂O, have been characterized by XRD, FT-IR, DTA-TG techniques and chemical analysis. The molar enthalpies of solution of Pb(BO₂)₂·H₂O and PbB₄O₇·4H₂O in 1 mol dm^?3 HNO₃(aq) were measured to be (?35.00 ± 0.18) kJ mol^?1 and (35.37 ± 0.14) kJ mol^?1, respectively. The molar enthalpy of solution of H₃BO₃(s) in 1 mol dm^?3 HNO₃(aq) was measured to be (21.19 ± 0.18) kJ mol^?1. The molar enthalpy of solution of PbO(s) in (HNO₃ + H₃BO₃)(aq) was measured to be ?(61.84 ± 0.10) kJ mol^?1. From these data and with incorporation of the enthalpies of formation of PbO(s), H₃BO₃(s) and H₂O(l), the standard molar enthalpies of formation of ?(1820.5 ± 1.8) kJ mol^?1 for Pb(BO₂)₂·H₂O and ?(4038.1 ± 3.4) kJ mol^?1 for PbB₄O₇·4H₂O were obtained on the basis of the appropriate thermochemical cycles.     

2MgO·2B2O3·MgCl2·14H2O在60℃水中的溶解及相转化动力学研究

用动力学方法研究了２ＭｇＯ·２Ｂ２Ｏ３·ＭｇＣｌ２·１４Ｈ２Ｏ在６０℃水中的溶解及相转化过程．通过对不同时间取出液相的化学分析及不同阶段分离出固相所作鉴定结果表明：该复盐呈不同步溶解,中间产物是ＭｇＯ·Ｂ２Ｏ３·４Ｈ２Ｏ和Ｍｇ（ＯＨ）２,最终转化产物是柱硼镁石（ＭｇＯ·Ｂ２Ｏ３·３Ｈ２Ｏ）．提出了溶解及相转化机理,给出了溶解和转化结晶动力学方程