1-甲氧基乙基-3-甲基咪唑甘氨酸离子液体的物理化学性质的研究

由于氨基酸基的独特性质,我们以甘氨酸作为阴离子,醚基咪唑基团作为阳离子合成了一种新型离子液体1-甲氧乙基-3-甲基咪唑甘氨酸[MOEMIM][Gly],并经过核磁共振氢谱、核磁共振碳谱和差示扫描量热进行表征。由于离子液体和水之间形成氢键导致传统的方法不能去除水的影响,所以在实验测定中,选用标准加入法在温度范围为298.15–338.15 K,每隔5 K测定离子液体[MOEMIM][Gly]的密度和表面张力。利用密度数据,计算得到离子液体[MOEMIM][Gly]的摩尔体积,并且摩尔体积随着温度的升高而增加,同时得到了热膨胀系数。根据离子液体[MOEMIM][Gly]的摩尔表面Gibbs自由能,改进了传统的Eötvös经验方程,使得方程具有更明确的物理意义,即截距C₀代表摩尔表面焓,它是一个与温度无关的常数,斜率则为摩尔表面熵,这表明改进的Eötvös方程不仅是一个经验方程,而且还是严格的热力学方程。另外,结合摩尔表面Gibbs自由能和改进的Eötvös方程,估算了离子液体的[MOEMIM][Gly]的表面张力,并与实验值进行比较,发现两者很好的一致。     

"分光光度法测定碘化铅溶度积常数"实验存在的问题及改进

针对"分光光度法测定碘化铅溶度积常数"实验测定方法中存在的问题,提出了改进方法。用改进后的方法测定碘化铅溶度积常数,减少了实验药品和污染,简化了实验环节和数据处理过程,使实验测定的数据更准确。并且根据热力学公式推导、计算和作图,给出了lnK_(sp)~θ与1/T关系的直线方程,可以判断不同温度时测试结果的准确程度。     

α-Cu_2Se精细结构的球差校正扫描透射电镜表征

目前学界对Cu_2Se低温α相的结构仍未认识清楚,而解决这一问题对理解Cu_2Se在相变过程中热电性能提升等特性具有重要意义。本文首次报道了由球差校正扫描透射电镜(STEM)拍摄到的沿■带轴的原子级分辨率高角环形暗场(HAADF)像,揭示了由Se原子以多种形式有序起伏产生的复杂结构。结合电子衍射图谱,分析了包含不同层数、通过相互组合构成α-Cu_2Se晶体的多种结构变体。使用QSTEM软件对构建的结构变体进行高分辨图像模拟,得到了与实验对应的HAADF像。该工作为更全面地理解α-Cu_2Se的结构提供了新的重要信息。     

多次碰撞条件下金阳离子诱导的甲烷碳―碳偶联

The reactivity of atomic metal cations toward CH₄ has been extensively investigated over the past decades. Closed-shell metal cations in electronically ground states are usually inert with CH₄ under thermal collision conditions because of the extremely high stability of methane. With the elevation of collision energies, closed-shell atomic gold cations (Au⁺) have been reported to react with CH₄ under single-collision conditions to produce AuCH₂⁺, AuH⁺, and AuCH₃⁺ species. Further investigations found that the ion-source-generated AuCH₂⁺ cations can react with CH₄ to synthesize C―C coupling products. These previous studies suggested that new products for the reaction of Au⁺ with CH₄ can be identified under multiple-collision conditions with sufficient collision energies. However, the reported ion-molecule reactions involving methane were usually performed under single- or multiple-collision conditions with thermal collision energies. In this study, a new reactor composed of a drift tube and ion funnel is constructed and coupled with a homemade reflectron time-of-flight mass spectrometer. Laser-ablation-generated Au⁺ ions are injected into the reactor and drift 120 mm to react with methane seeded in the helium drift gas. The reaction products and unreacted Au⁺ ions are focused through the ion funnel and accumulate through a linear ion trap and are then detected by a mass spectrometer. In the reactor, the pressure is approximately 100 Pa, and the electric field between the drift tube and ion funnel can regulate the collision energies between ions and molecules. The reaction of the closed-shell atomic Au⁺ cation with CH₄ is investigated, and the C―C coupling product AuC₂H₄⁺ is observed under multiple-collision conditions with elevated collision energies. Density functional theory calculations are performed to understand the mechanism of the coupling reaction (Au⁺+ 2CH₄ → AuC₂H₄⁺ + 2H₂). Two pathways involving Au―CH₂ and Au―CH₃ species can separately mediate the C―C coupling process. The activation of the second C―H bond in each process requires additional energy to overcome the relatively high barrier (2.07 and 2.29 eV). Ion-trajectory simulations under multiple-collision conditions are then conducted to determine the collisional energy distribution in the reactor. These simulations confirmed that the electric fields between the drift tube and ion funnel could supply sufficient center-of-mass kinetic energies to facilitate the C―C coupling process to form AuC₂H₄⁺. The following catalytic cycle could then be postulated: $\mathrm{AuC}_{2} \mathrm{H}_{4}^{+}+\mathrm{CH}_{4} \stackrel{\Delta}{\longrightarrow} \mathrm{AuCH}_{4}^{+}+\mathrm{C}_{2} \mathrm{H}_{4}, \mathrm{AuCH}_{4}^{+}+\mathrm{CH}_{4} \stackrel{\Delta}{\longrightarrow} \mathrm{AuC}_{2} \mathrm{H}_{4}^{+}+2 \mathrm{H}_{2}$, and $\mathrm{CH}_{4} \stackrel{\mathrm{Au}^{+}, \Delta}{\longrightarrow} \mathrm{C}_{2} \mathrm{H}_{4}+2 \mathrm{H}_{2}$. Thus, this study enriches the chemistry of both gold and methane.     

Rhenium(I) methoxo carbonyl complexes containing tetraphosphine or triphosphine ligands; facile separation and X-ray crystallographic studies of d/l- and meso-[{Re2(μ-OMe)2(CO)6}2(μ,μ′-1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetra-phosphadecane)]

Reaction of the activated mixture of Re₂(CO)_10, Me₃NO and MeOH with a 1:1 mixture of rac (d/l)- and meso-1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane (hptpd) yields a mixture of (d/l)- and meso-[{Re₂(μ-OMe)₂(CO)₆}₂(μ,μ′-hptpd)] 1. The diastereomers can be easily separated by selective dissolution of d/l-1 in benzene, and give clearly distinguishable ¹H- and ³¹P-NMR spectra. The fluxional behavior of d/l-1 in solution has been studied by variable-temperature ¹H- and ³¹P-{¹H}-NMR spectroscopy. The crystal structures of both d/l- and meso-1 have been determined. Both molecules consist of two {Re₂(μ-OMe)₂(CO)₆} moieties which are bridged by the two P---CH₂---CH₂---P moieties of the hptpd ligand. Whilst the molecules of meso-1 possess crystallographic i-symmetry, those of d/l-1 do not have any crystallographic symmetry. These diastereomers therefore give clearly distinguishable Raman spectra in the solid state. Reaction of tris[2-(diphenylphosphino)ethyl]phosphine (tdppep) with the activated mixture affords the complex [{Re₂(μ-OMe)₂(CO)₆}(μ,η²-tdppep)] 2, and the analogous reaction involving bis[2-diphenylphospinoethyl)phenylphosphine (triphos) gives [{Re₂(μ-OMe)₂(CO)₆}(μ,μ′,η³-triphos){Re₂(CO)₉}] 3 and [{Re₂(μ-OMe)₂(CO)₆}(μ,η²-triphos)] 4.     

星形胶束自由能和聚集数的理论分析

ＡＢ型嵌段聚合物在选择性溶剂中将发生微相分离,形成一种球形胶束[1].所谓选择性溶剂是指此溶剂仅能溶解共聚物中某一链段,而对另一链段则为不良溶剂.对这一体系的实验研究是从80年代兴起的,主要采用现代测试技术来表征形成胶束的回转半径[2],动力学半径[3]、聚集数[4]和临界胶束浓度[5].从分子图景上看来,这种球形胶束包括两部分,内核(Ｃｏｒｅ)为密堆砌的链段Ａ;壳层(Ｃｏｒｏｎａ)为溶涨的链段.Ｈｅｌｆａｎｄ等[6]最早利用数值计算法来研究嵌段聚合物在本体中的微相分离的问题;Ｌｅｉｂｌｅｒ等[7]将此方法引入嵌段聚合物/均聚物体系.…     

Premicellar aggregation of amphiphilic molecules

We revisit the problem of amphiphilic aggregation using a simple two-state (monomer-aggregate) thermodynamic model, which allows the study of metastable aggregates of variable size. A sequence of well separated concentrations emerge: c(1), where a metastable aggregated state appears; c(2), above which an appreciable amount of metastable aggregates forms; and c(3), where the aggregated state becomes stable. Of these, c(3) is shown to correspond to the critical micelle concentration (cmc) as commonly measured in macroscopic experiments. Thus, appreciable premicellar aggregation is predicted in the concentration range between c(2) and c(3). We show that, so long as the micelles are not too large, the extent of premicellar aggregation is much larger than that expected from mere finite-size effects. It stems from the variability of the micelle size and the small free energy difference between the metastable state, containing monomers and aggregates, and the pure monomeric one. The aggregate size is found to weakly change with concentration below and above the cmc. The existence of premicellar aggregates and their concentration-insensitive size are in agreement with a recent experiment.     

Über die Berechnung der Elektronenenergie eines Moleküls aus dem Erwartungswert der kinetischen Energie

Knowing the mean value of the electronic kinetic energy T(X _i ) of a molecule as a function of the nuclear coordinates X _i , it is shown that the electronic energy can be uniquely determined by the virial theorem . The result is .

---

---

Herrn Prof. R. G. Parr danke ich für die Fragestellung und Diskussionen. Herrn Prof. G. Weber und Herrn Dr. R. Güther möchte ich ebenfalls für Diskussionen danken.     

含酯基Gemini表面活性剂在有机醇-水体系中的胶束热力学及聚集行为

采用电导法研究了不同温度下含酯基Gemini表面活性剂在纯水和在质量分数为10%的甲醇-水(MAWR),乙二醇-水(EG-WR),丙三醇-水(GL-WR)四种体系中的集聚行为和胶束热力学;聚集行为参数包括临界胶束浓度(cmc)和抗衡离子的解离程度(α)以及胶束的热力学参数,包括标准吉布斯自由能(ΔG_m~o)、吉布斯迁移自由能(ΔG_(trans)~o)、吉布斯烷基链胶束化自由能(ΔG_(tail)~o)、标准焓变(ΔH_m~o)和标准熵变(ΔS_m~o),均被计算和讨论。研究表明在所有的研究体系中,cmc值随着疏水链的增加而减小,随着加入的醇结构中羟基数目的增加而增大,随温度的升高先变小,后变大呈U字形;胶束化过程都是自发进行的,并且在293.15 K下,胶束化过程是吸热的,在293.15 K上,胶束化过程是放热的;通过稳态荧光光谱法研究了表面活性剂在纯水、有机醇-水混合溶液中的微极性,结果表明,在相同溶剂中,随着烷基链长度的增加,溶液微环境的疏水性越强;对于相同的Gemini表面活性剂,随着加入含羟基数目越多的醇,其微环境的疏水性越强。并研究了Gemini表面活性剂在混合体系中形成胶束过程的焓-熵补偿曲线。     

Additivity of the effect of ligand parameters on the redox potential of the Cu(II)/Cu(I) pair

The redox potential of Cu(II)/Cu(I) complexes with polydentate ligands can be calculated from the equation (V relative to the normal hydrogen electrode). In this paper, we give 13 E_i parameters, quantitatively reflecting various electronic and steric properties of the ligands.Slovak PoIytechnicaI Institute, Bratislava. Translated from Teoreticheskaya i Éksperi-mental'naya Khimiya, Vol. 27, No. 3, pp. 34l–345, May–June, 1991. Original article submitted February 18, l991.     

Character of intermediate radicals in homolytic isomerization of cyclic acetals and their heteroanalogs

Conclusions Employing the EPR method and 2-methyl-2-nitrosopropane as the spin trap, we recorded the formation of the radicals (n = 1 and 2; X = O, N, or a chain composed of C and O atoms; R = H or alkyl) during the photolysis of acetals and their heteroanalogs in the presence of di-tertbutyl peroxide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2097–2099, September, 1976.The authors are indebted to A. Sh. Mukhtarov for assistance in running the experiments.     

Protonation and deprotonation of hydroxamic acids. An MO ab initio study

Ab initio molecular orbital calculations with 4-31G//4-31G, 6-31G^*//4-31G and 6-31+G//4-31G basis sets have been used to examine the structure, relative energy, protonation and deprotonation of a series of seven hydroxamic acids in the gas phase. The results show that hydroxamic acids are predominantly in the E-TS form and that the most probable protonation site is the carbonyl oxygen atom, while deprotonation proceeds by loss of NH hydrogen.     

Adsorption of oligooxypropylenated amines at the aqueous solution—air interface: Homologous series of piperidine and morpholine derivatives

The surface tension isotherms for pure oligooxypropylenated piperidine and morpholine at the aqueous solution—air interface were determined and interpreted. The surface excess concentration, Γ, the surface area per molecule, A, and the standard free energy of adsorption, ΔG°, were calculated according to a new empirical adsorption equation. The standard free energy contribution for the oxypropylene group (PO) in morpholine derivatives,ΔG° (PO) = −3.34 kJ mol⁻¹, is substantially lower than that for the PO group located in the piperidine derivatives, i.e. ΔG° (PO)= −3.12 kJ mol⁻¹.     

直线型l-CnH(n=5,6)自由基与氧气反应机理的理论研究

为了探索更长的碳链自由基l-C_nH与O₂反应的机理, 在CCSD(T)/CC-PVTZ+ZPVE//B3LYP/6-311++G(d,p)的计算水平下, 讨论了当n=5,6时, l-C_nH+O₂的各个异构化反应通道. 当n=5时, 主要反应通道为碳迁移过程, 生成主要产物为P2(CO₂+C₄H); 当n=6时, 碳-氧交换[产物为P1(CO+HC₅O)]和氧迁移过程[产物为P3(³O+HC₆O)]均为主要通道, 并具有很高的竞争性. 将所得结构与l-C_nH(n≤4)+O₂的反应机理进行了对比.     

Interactions of Cationic Surfactant Cetyl-trimethyl ammonium bromide with Ammonium nitrate: Surface and Thermodynamic Studies

The study of interactions between surfactant and salt in aqueous solutions has attracted significant interest in recent years because of their widespread applications and relatively complex behavior. This work reports the systematic study of surface phenomenon and self-aggregation behavior of cationic surfactant cetyltrimethyl ammonium bromide (CTAB) with ammonium nitrate (NH\begin{document}$ _4 $\end{document}NO\begin{document}$ _3 $\end{document}) salt. Surface and thermodynamic properties of cationic surfactant CTAB with NH\begin{document}$ _4 $\end{document}NO\begin{document}$ _3 $\end{document} were investigated at different temperatures using different techniques such as conductometry and surface tensiometery. The surface tension measurement was carried out to find out the critical micelle concentration, free energy of adsorption, free energy of micellization, minimum area per molecule, and surface excess concentration. The study reveals that the process of micellization is spontaneous and exothermic in nature. Conductance measurement was carried out to determine critical micelle concentration, degree of ionization and degree of counter ion binding. Addition of NH\begin{document}$ _4 $\end{document}NO\begin{document}$ _3 $\end{document} to the surfactant solutions increase the values of degree of ionization and degree of counter ion binding, although it lowers the values of critical micelle concentration showing that the process of micellization is more favorable and spontaneous. The study is very helpful to develop better understanding about interaction between electrolyte and surfactant, which are used in many applications and in different processes (e.g., pharmaceutical, industrial foaming, drug solubilization, oil recovery, and medium for metal nanoparticle formation).     

CSSP2: an improved method for predicting contact-dependent secondary structure propensity

The calculation of contact-dependent secondary structure propensity (CSSP) has been reported to sensitively detect non-native β-strand propensities in the core sequences of amyloidogenic proteins. Here we describe a noble energy-based CSSP method implemented on dual artificial neural networks that rapidly and accurately estimate the potential for the non-native secondary structure formation in local regions of protein sequences. In this method, we attempted to quantify long-range interaction patterns in diverse secondary structures by potential energy calculations and decomposition on a pairwise per-residue basis. The calculated energy parameters and seven-residue sequence information were used as inputs for artificial neural networks (ANNs) to predict sequence potential for secondary structure conversion. The trained single ANN using the >(i, i ± 4) interaction energy parameter exhibited 74% accuracy in predicting the secondary structure of test sequences in their native energy state, while the dual ANN-based predictor using (i, i ± 4) and >(i, i ± 4) interaction energies showed 83% prediction accuracy. The present method provides a simple and accurate tool for predicting sequence potential for secondary structure conversions without using 3D structural information.     

Studies on potentiometric stripping analysis

Theoretical and experimental investigations have been made on the method of potentiometric stripping analysis. By solving Fick's second law of diffusion for the metal in the amalgam, it was found that τ = C⁰_Rl/k[Ox], where τ is the elapsed time, l is the thickness of the mercury film, C⁰_R is the concentration of the metal in the amalgam, [Ox] is the concentration of the oxidant in the solution and k is a constant. Since C⁰_R is proportional to the concentration of that particular ion in the solution under given pre-electrolysis conditions, the relations given by the equation above can all be verified experimentally. The equation of the potential—time curve and the effect of complex formation on the elapsed time were also investigated and discussed. In the absence of complexation reactions in the solution and with proper control of the concentration of the oxidant, the lowest limit of detection for Pb was found to be 10⁻¹²M for a 4-min pre-electrolysis, with dissolved oxygen as oxidant.     

Quantal state-to-state H-atom exchange cross sections of low energy 1H (v= 0) + Br reactions

The dynamics of the IH + Br heavy-light + heavy system is treated using the Born-Oppenheimer-type separation between the light and the heavy nuclear motions. The hydrogenic wavefunctions, that describe the H-nucleus motion for clamped I and Br nuclei, provide the potential energy curves and couplings that govern the I-Br relative motion. The Hatom exchange cross sections in the reactive collision: IH(v= 0,j) + Br → I + HBr(v′,j′) are found to strongly depend upon j and to be large only for v′ = 1 with j′ = 16–20 and for v′ = 2 with j′ = 8–11. The present results are compared to our previous estimates, to results of classical trajectory calculations and to available experimental data.     

A simple model for polysoaps' thread-like aggregates

The equilibrium polymerization, a model for one-dimensional reversible aggregates is used under conditions of theta and bad solvent to describe thread-like aggregates of polysoaps. In two dimensions, the aggregate size distribution decreases always more slowly than an exponential distribution and the dependence of the mean aggregate size L on the density φ and end-cap energy E of the polysoap cylindrical micelle is of the form L[φexp(E/KT)]^δ with δ<1/2. On the other hand, in three dimensions in the bad solvent regime, the dependence of L on φ becomes exponential explaining the high φ dependence of the viscosity in experimental results.     

A diffusing wave spectroscopy study of the dynamics of interactions between high methoxyl pectin and sodium caseinate emulsions during acidification

A non-invasive technique, diffusing wave spectroscopy (DWS), and traditional dynamic light scattering (DLS) were used to study the interactions of high methoxyl pectin (HMP) with sodium caseinate-stabilized emulsion droplets. At pH 6.8, the droplet size measured by DLS did not change as a function of HMP concentration (up to 0.3%). However, the droplet diameter measured by DWS kept relatively constant up to 0.07% HMP after which it showed drastic increases. The turbidity parameter 1/l* decreased with HMP concentration and levelled off at 0.07% HMP, indicating that the system underwent reorganization and reached equilibrium at 0.07% HMP. During acidification at pH 5.4, right before the pH of aggregation of control emulsions, all emulsions containing 0.05–0.2% HMP showed an increase of 1/l*. This increase indicated the interaction of HMP with sodium caseinate at the interface. Emulsions containing 0.05 and 0.1% HMP also showed destabilization, and the pH of destabilization depended on the concentration of HMP. Sufficient amounts of HMP (0.2%) stabilized the caseinate-coated oil droplets, and the mean square displacement slope was close to 1 throughout, indicating free diffusion of emulsion droplets.