Reliable evaluation of temperature-independent parameters in correlation of vapour–liquid equilibrium data

A new algorithm/program has been elaborated for simultaneous processing of different sets of vapour–liquid equilibrium data. The program was tested with six binary hexane + isomeric pentanol systems, each of them measured at three different isobaric conditions and one isothermal system of tert-butyl-methyl-ether + 2-methyl-2-propanol measured at three different temperatures. The correlation uses the maximum likelihood method, taking into account real behaviour of vapour phase. The parameters obtained are valid within the whole temperature range of the data, and are consistent in comparison with those obtained from individual correlations of isobars or isotherms. Results are presented for the Wilson and NRTL equations.     

pH,Definition and measurement at high temperatures

In this review paper, the NBS scale and its limitations are briefly discussed. The magnitude of liquid junction potentials and some calculated values are presented. The use of a molality scale for hydrogen electrode concentration cells at high temperatures is described, and results from measurements on ionization equilibria are summarized. Use of this scale is also recommended for certain circumstances with cells without liquid junction. As an alternative activity scale, use of the Pitzer ion-interaction treatment for ions is recommended for special cases. Finally, reference data are presented for _±HCl in HCl(aq) to 350°C and (HCl+NaCl)(aq) to 200°C that were derived by use of the Pitzer ion-interaction treatment.Presented at the Second International Symposium on Chemistry in High Temperature Water, Provo, UT, August 1991.     

Spectrochemical Properties of Noncubical Transition Metal Complexes in Solutions. XIV. Angular Overlap Studies of bis(Salicylidene-2-aminothiazole)Copper(II) in Various Solvents

The copper(II) complex [Cu(sat)], where Hsat is salicylidene-2-aminothiazole (bidentate Schiff - base), was studied in variety of solvents. In the solid state, the complex is black. It has been characterized by elemental analysis, solubility in common solvents, molar conductivity, and ultraviolet (UV) and visible (Vis) spectroscopy. The complex is easily soluble in common solvents such as chloroform, dimethylformamide, dimethyl sulfoxide, and 1,4-dioxane. The known crystal structure of similar compounds shows planar coordination geometry for the copper center. Combined multitechnique experiments have been applied to confirm the structure of the complex in solutions. The molar conductivities indicate their nonelectrolyte properties in all these solvents. The spectroscopic measurements were used to study the coordination properties of donoratoms and their bonding abilities.     

Mechanistic aspects of the Wolff-Kishner reaction. V. The cation effect on the reaction of benzophenone hydrazone in butyl carbitol and decyl alcohol

The rate of the Wolff-Kishner reaction of benzophenone hydrazone in butyl carbitol increases as the cation of the alkoxide base is varied in the order K>Na>Li>Mg. The replacement of butyl carbitol by 1-decanol also accelerates the reaction, and an additional increase is caused by the presence of crown ether. On the basis of changes in the activation parameters, it is concluded that the reactivity of the hydrazone anion increases as the contact ion pair becomes more fully solvated and dissociated.     

毛细管电色谱中双电层叠加的研究

通过流动相中电解质浓度对毛细管电色谱柱效能的流动相平均线速度的影响，研究了ＣＥＣ中双电层叠加现象。提出选择合适电解质组成的浓度及在制备色谱柱过程中避免细小和破碎的固定相颗粒进入柱中，以有效地减小双电层叠加作用。     

线性分析法来解热脱附动力学参数

TPD方法是研究表面常规手段之一.对于如何从实验结果获得正确的脱附动力学参数,已有不少工作发表。然而,现有方法均存在一定的适用范围,尤其是重叠谱解叠,仍然没有很好地解决。本文介绍的线性分析法,不仅适用于简单的一级和二级脱附TPD谱的解析,而且也适用于重叠谱解叠,从而为实验上确定动力学级数和复杂谱解叠提供了依据。     

Ab initio calculations of vibronic activity in phosphorescence microwave double resonance spectra of p-dichlorobenzene

The phosphorescence spectrum of p-dichlorobenzene has been calculated using multiconfiguration self-consistent-field wave functions and the quadratic response technique. Attention has been paid to the intensity distribution of the singlet–triplet (³B_1u¹A_g) transition through a number of vibronic subbands. The second order spin–orbit coupling (SOC) contribution to the spin splitting of the ³B_1u (^3*) state is found to be almost negligible, and the calculations therefore provide a good estimate for the zero-field splitting (ZFS) parameters based only on the electron spin–spin coupling expectation values. Nuclear quadrupole resonance constants for the different Cl isotopes are also calculated to accomplish the ZFS assignment. The electric dipole activity of the spin sublevels in the triplet–singlet transitions to the ground-state vibrational levels is estimated by calculations of derivatives using distorted geometries which are shifted from the equilibrium position along different vibrational modes. A vibrational analysis of the phosphorescence spectrum, based on the SOC-induced mixing of the singlet and triplet states calculated along different vibrational modes, provides reasonable agreement with experimental data.Acknowledgment O. R.-P. would like to thank the European MOLPROP network for support. The authors thank Alexander Baev for fruitful discussions. This work was supported by the Swedish Royal Academy of Science (KVA).     

Multipole expansion of diatomic overlap

A systematic extension of Ruedenberg's expansion formula is applied to evaluate two-electron integrals occurring in calculations on molecular structure. Minimum STO basis sets are used for all SCF-calculations within the framework of the MEDO-method (Multipole Expansion of Diatomic Overlap). The errors due to this approximation scheme are almost negligible compared to those introduced by the truncated basis set: LiH, Li₂ and N₂ are chosen as examples.     

Optimization of auxiliary basis sets for the LEDO expansion and a projection technique for LEDO-DFT

We present a systematic procedure for the optimization of the expansion basis for the limited expansion of diatomic overlap density functional theory (LEDO-DFT) and report on optimized auxiliary orbitals for the Ahlrichs split valence plus polarization basis set (SVP) for the elements H, Li--F, and Na--Cl. A new method to deal with near-linear dependences in the LEDO expansion basis is introduced, which greatly reduces the computational effort of LEDO-DFT calculations. Numerical results for a test set of small molecules demonstrate the accuracy of electronic energies, structural parameters, dipole moments, and harmonic frequencies. For larger molecular systems the numerical errors introduced by the LEDO approximation can lead to an uncontrollable behavior of the self-consistent field (SCF) process. A projection technique suggested by L?wdin is presented in the framework of LEDO-DFT, which guarantees for SCF convergence. Numerical results on some critical test molecules suggest the general applicability of the auxiliary orbitals presented in combination with this projection technique. Timing results indicate that LEDO-DFT is competitive with conventional density fitting methods.     

Surface characterization of macroporous glycidyl methacrylate based copolymers by inverse gas chromatography

Two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), PGME, with different porosity parameters were synthesized by suspension copolymerization and modified by ring-opening reaction of the pendant epoxy groups with ethylene diamine, EDA. Inverse gas chromatography at infinite dilution was used for the determination of adsorption properties of PGME, and copolymer modified with ethylene diamine, PGME-en. Thermodynamic parameters of adsorption, dispersive components of the surface free energies, and the acid/base constants for the copolymer samples were calculated. The calculated dispersive surface energy values, , for PGME and PGME-en are comparable with the literature data for nonconductive polymers.