阳树脂再生度对水汽系统氢电导率监测准确性的影响研究

水汽系统氢电导率监测用氢交换柱附加误差超标是造成氢电导率测量不准确的主要原因，而氢交换柱附加误差超标主要源于阳树脂的再生度低。理论分析和研究结果表明，氢交换柱附加误差与阳树脂再生度及水样Cl^-浓度均有关系，再生度越低，Cl^-浓度越高，氢交换柱附加误差就越大。对于超临界水汽系统氢电导率测量用氢交换柱，为了保证附加误差满足不大于5%的标准要求，建议控制树脂再生度在85%以上。阳树脂再生度取决于再生工艺，动态再生和电再生的效果要比静态浸泡再生好，可以保证树脂的再生度和氢交换柱的附加误差满足要求。     

活泼氢的核磁共振氢谱

核磁共振氢谱是有机化合物结构表征中最常使用的波谱方法之一,提供了有机化合物质子的化学位移、积分面积和耦合裂分等信息。常见的活泼氢是与氧、氮和硫共价相连的氢原子,存在着快速交换机制,与碳上的氢有显著的差异。在不同条件下活泼氢化学位移不固定、峰形多变并且耦合裂分情况复杂。本文探讨了如何通过核磁共振氢谱解析活泼氢,培养学生对谱图进行观察、分析以及结构推导的能力。     

球钯材料填充柱中氢-氘交换的计算机模拟

本文结合球体颗粒交换模型(SPEM)与气-固表面交换模型设计了氢-氘交换反应模型, 采用FORTRAN语言进行计算机编程模拟, 研究了钯材料粒径、分离柱长度、填料密度、气体流速和温度等因素对氢氘交换反应的影响。结果表明:通过降低气体流速, 增大金属材料目数、填料密度、交换柱长, 以及升高温度, 可以提高交换速率;而在满足一维速率方程的条件下, 柱径的大小不影响交换反应过程。     

球钯材料填充柱中氢-氘交换的计算机模拟

本文结合球体颗粒交换模型(SPEM)与气-固表面交换模型设计了氢-氘交换反应模型,采用FORTRAN语言进行计算机编程模拟,研究了钯材料粒径、分离柱长度、填料密度、气体流速和温度等因素对氢氘交换反应的影响。结果表明:通过降低气体流速,增大金属材料目数、填料密度、交换柱长,以及升高温度,可以提高交换速率;而在满足一维速率方程的条件下,柱径的大小不影响交换反应过程。     

钠离子取代对气相分子氢氘交换反应的影响

用质谱学方法测定分子的氢氘交换反应过程和结果是研究蛋白质分子等生物体系的分子构象,如蛋白质折叠状态的常用方法之一．本文利用线型离子阱．飞行时间质谱技术,在气相中测定了由不同个数钠离子所取代的简单多肽分子——五联丙氨酸（5Ala-nH＋nNa）．H^＋,,n=2,3,4,5的氢氘交换反应情况,得到了由不同个数钠离子取代的分子离子的氢氘交换反应速度以及交换的氢氘数量等,并研究了钠离子个数对分子氢氘交换反应的影响．结果表明,在本工作的实验条件下,钠离子的取代将影响分子离子的氢氚交换反应．当钠离子数为2时,（5Ala-2H＋2Na）．H^＋分子离子很难发生氢氘交换反应;当钠离子数增加时,对于（5Ala-3H＋3Na）．H^＋,（5Ala-4H＋4Na）．H^＋,和（5Ala-5H＋5Na）．H^＋等,分子的氢氘交换反应速度会加快．这可能是由于钠离子的取代导致了分子离子的构型以及分子的质子亲和势发生了显著的改变,因此影响它们的氢氘交换反应．此外,我们还研究了线型四极场的q值对离子氢氘交换反应的影响,发现对于某种离子,当其对应的四极场q值低于0．8时,对各种离子的交换反应速度影响不大,但当q值接近第一稳定区图的边界点,即当q接近0．908时,对某些离子的交换反应速度影响很明显．q值对离子的交换反应速度影响可以用离子的运动速度加快而导致碰撞反应能量增加来解释．     

硼氢阴离子交换树脂的制备及其对羰基、酰氯化合物的还原

Gibson和Bailey首次应用Cl型季铵型强碱性阴离子交换树脂与NaBH_4交换,制备了硼氢阴离子交换树脂还原剂(简称BER)。     

电阻型湿敏材料的核磁共振研究

利用核磁共振氢谱研究了不同湿度和温度条件下聚乙烯亚胺，聚乙烯铵盐及环氧乙烷３种电阻型湿敏材料，通过化学位移变化分析了感湿机理，指出３种材料中的活泼氢和水作用后能形成新的活泼氢，新旧活泼氢可发生快速交换现象，并产生带电离子，因而材料的电阻值随湿度的增加而大幅度地降低。     

H+NH3反应势能面的量子化学研究

本文采用UCCSD(T)/aug-cc-pVTZ方法研究了H NH3反应势能面,获得了夺氢反应和交换反应过渡态的的几何结构和振动频率。夺氢反应的过渡态具有Cs对称性,其能垒为61.92 kJ/mol。交换反应的过渡态具有C3v对称性,其能垒为39.69 kJ/mol。H NH3发生形成Td对称性的反应中间体NH4里德堡自由基。与夺氢反应相比,交换反应具有更低的反应能垒,并且NH4自由基在反应中可形成长寿命的共振态,和夺氢反应形成竞争关系,因此在H NH3反应的量子动力学研究中必须同时考虑这两类反应。本文还采用更大的基组aug-cc-pVQZ和aug-cc-pV5Z研究了势能面对基组的收敛行为。     

新型锍类化合物的合成及其DNA复合性能

报道了一类新型的以锍离子提供正电荷的阳离子脂质体的合成。以四氢噻吩和四氢噻喃为原料,在四氟硼酸银体系中与链状碘代脂肪烷烃经取代反应制得硫正离子化合物,产物用氯离子交换树脂交换得阴离子为氯离子的8种新型的链状锍类鎓氯盐脂质体化合物,其结构经~1H NMR,~(13)C NMR,FT-IR和HR-MS(ESI)表征。凝胶电泳阻滞实验表明该类锍化合物具有和DNA聚合并形成复合物的能力,随着脂肪链的增长,复合能力增强。     

磷钼酸四氢三铵的制备及其交换性能

磷钼酸四氢三铵的制备及其交换性能臧二乐，梁树权（北京农业大学应用化学系北京１０００９４）（中国院学院化学研究所北京）关键词磷钼酸四氢三铵，制备，离子交换性能通式为Ｍ＿ｎＸＹ＿（１２）Ｏ＿（４０）·ｐＨ＿２Ｏ（其中Ｍ为一价阳离子；Ｘ为Ｐ、Ａｓ、Ｓｉ、Ｇ...     

Additivity and transferability of exchange energy

Exchange energy of molecules at equilibrium geometries is shown to be highly independent of the basis set and nearly equal to the sum of the exchange energies of isolated atoms. Furthermore, molecular exchange can be predicted along a chemical series with high accuracy in terms of empirical exchange contributions associated to the constituent atoms, whose values, obtained by fitting, are similar to those of the isolated atoms. It is concluded that molecular exchange is essentially a sum of atomic contributions whose differences from those of the isolated atoms are small and characteristic of the neighboring atoms. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Base-Catalyzed Keto-Enol Tautomerism of Diazepam

The hydrogens at 3-position of diazepam, a frequently prescribed anxiolytic drug worldwide, undergo an efficient exchange with deuterium atoms in alkaline deuterated methanol. The position of deuterium exchange is confirmed by proton nuclear magnetic resonance and mass spectral analyses. A base-catalyzed keto-enol tautomerism is proposed to be responsible for the observed deuterium exchange. This finding has been applied to the preparation of tritium-labeled diazepam in which only aromatic protons are labeled with tritium atoms. A tritium-labeled diazepam lacking tritium atoms at 1 and 3 positions is valuable as a substrate for quantitative metabolism studies.     

State of Chromium in Solid Solutions of Multicomponent Bismuth Niobates with Pyrochlore Structure

Magnetic susceptibility of solid solutions of multicomponent bismuth niobates with pyrochlore structure containing chromium atoms was studied. The parameters determining the state of chromium atoms and the exchange coupling between the paramagnetic atoms were calculated. The best agreement between the experimental and theoretically calculated magnetic moments of the chromium atoms is observed on the condition that all the chromium atoms in the Bi₂MgNb₂O₉ structure are in the form of ferromagnetic exchange-coupled dimers with an exchange parameter J 18 cm^{- 1}.     

Does the Sign of the Cu–Gd Magnetic Interaction Depend on the Number of Atoms in the Bridge?

Several theoretical investigations with CASSCF methods confirm that the magnetic behavior of Cu–Gd complexes can only be reproduced if the 5d Gd orbitals are included in the active space. These orbitals, expected to be unoccupied, do present a low spin density, which is mainly due to a spin polarization effect. This theory is strengthened by the experimental results reported herein. We demonstrate that Cu–Gd complexes characterized by Cu–Gd interactions through single‐oxygen and three‐atom bridges consisting of oxygen, carbon, and nitrogen atoms, present weak ferromagnetic exchange interactions, whereas complexes with bridges made of two atoms, such as the nitrogen–oxygen oximato bridge, are subject to weak antiferromagnetic exchange interactions. Therefore, a bridge with an odd number of atoms induces a weak ferromagnetic exchange interaction, whereas a bridge with an even number of atoms supports a weak antiferromagnetic exchange interaction, as observed in pure organic compounds and also, as in this case, in metal–organic compounds with an active spin polarization effect.     

Studies on Natural CXN Zeolite： Modification, Framework De-alumination and Ion-exchange

A natural CXN zeolite (stilbite, type code-STI) discovered in China was modified with NH4^ exchange by using ammonium salt and calcinations (procedure Ⅰ), or with NH4 exchange followed by treatment with acid (procedure Ⅱ). The coordination state of Si and A1 atoms in the framework, the property of ion exchange, and the adsorption of the H-STI zeolite samples prepared by different modification procedure were investigated with XRD,EDX,^29Si and ^27Al MAS NMR, Ag^ ion exchange and Ne adsorption. The results of the investigations indicate that different procedure of the modification made variety on the distribution of the framework Si atoms and A1 atoms,the content of non-framework aluminum, and the blocking channels and the shielding effect to the positions of the exchangeable cations. The H-STI zeolite prepared by the procedure Ⅱ possesses high ion exchange capacity, open and perfect pore system, and high thermal stability.     

Influence of non-bridging donor atoms on the value of exchange interaction in binuclear Cu<Superscript>II</Superscript> complexes with bis-hydrazones based on 2,6-diformylphenol

The quantum chemical simulation of exchange interaction according to the broken symmetry approach was performed for a series of binuclear Cu^II complexes containing the asymmetric exchange moiety based on bis-hydrazones of 2,6-diformylphenol. The calculated values were compared between themselves and with the experimental values of the exchange parameter 2J for the binuclear copper(II) complexes with bis-hydrazones based on 2,6-diformylphenol in order to reveal the influence pattern of the nature of nonbridging donor atoms X (O, N, S, and Se) onto the exchange interaction. The strength of exchange interaction of the antiferromagnetic type depends significantly on the nature of nonbridging donor atoms, increasing in the series of X = O, NH, S, and Se.     

粉状白钨酸的研究(Ⅹ)——粉状白钨酸的离子交换性能

通过粉状白钨酸和黄钨酸的离子交换性能的测定,比较了它们之间化学活性的相对大小。用动态法(交换柱法)测得了它们的离子交换容量,计算了与钨原子相联的羟基数目。并用静态法(振荡平衡法)测定了白钨酸对不同阳离子的交换情况及各种鸽酸的pH滴定曲线。     

Probing the porosity of cocrystallized MCM-49/ZSM-35 zeolites by hyperpolarized 129Xe NMR

One- and two-dimensional 129Xe NMR spectroscopy has been employed to study the porosity of cocrystallized MCM-49/ZSM-35 zeolites under the continuous flow of hyperpolarized xenon gas. It is found by variable-temperature experiments that Xe atoms can be adsorbed in different domains of MCM-49/ZSM-35 cocrystallized zeolites and the mechanically mixed counterparts. The exchange of Xe atoms in different types of pores is very fast at ambient temperatures. Even at very low temperature two-dimensional exchange spectra (EXSY) show that Xe atoms still undergo much faster exchange between MCM-49 and ZSM-35 analogues in the cocrystallized zeolites than in the mechanical mixture. This demonstrates that the MCM-49 and ZSM-35 analogues in cocrystallized zeolites may be stacked much closer than in the physical mixture, and some parts of intergrowth may be formed due to the partially similar basic structure of MCM-49 and ZSM-35.     

Spin-orbit relativistic long-range corrected time-dependent density functional theory for investigating spin-forbidden transitions in photochemical reactions

A long-range corrected (LC) time-dependent density functional theory (TDDFT) incorporating relativistic effects with spin-orbit couplings is presented. The relativistic effects are based on the two-component zeroth-order regular approximation Hamiltonian. Before calculating the electronic excitations, we calculated the ionization potentials (IPs) of alkaline metal, alkaline-earth metal, group 12 transition metal, and rare gas atoms as the minus orbital (spinor) energies on the basis of Koopmans' theorem. We found that both long-range exchange and spin-orbit coupling effects are required to obtain Koopmans' IPs, i.e., the orbital (spinor) energies, quantitatively in DFT calculations even for first-row transition metals and systems containing large short-range exchange effects. We then calculated the valence excitations of group 12 transition metal atoms and the Rydberg excitations of rare gas atoms using spin-orbit relativistic LC-TDDFT. We found that the long-range exchange and spin-orbit coupling effects significantly contribute to the electronic spectra of even light atoms if the atoms have low-lying excitations between orbital spinors of quite different electron distributions.     

Reactive collisions in quadrupole cells. 2. H/D exchange reactions of enolate ions with CH3od and C2H5OD

The H/D exchange reactions of enolate ions with CH₃OD and C₂H₅OD at low collision energies in the quadrupole collision cell of a hybrid tandem BEqQ mass spectrometer have been studied. The optimum parameters for exchange were elucidated using the enolate ion of acetone as a test reactant ion. With the exception of the enolate ions of 2,4-pentanedione and dimethylmalonate, all the enolate ions studied underwent exchange with CH₃OD and C₂H₅OD. Ion signals were observed corresponding to exchange of from one to all of the enolic hydrogen atoms. The H/D exchange reaction was more facile with C₂H₅OD as the reagent gas, and the results with this gas clearly permit a count of the number of enolic hydrogen atoms present in the molecule.