Rotational analysis of 3664 Å band of NiCl

Nickel chloride was excited in a high frequency discharge source and the band at 3664 Å was photographed at an inverse dispersion of 0.59 Å/mm on a two metre plane grating spectrograph. The rotational analysis was carried out and the molecular constants of the upper state are reported. The rotational isotopic shifts due to³⁷Cl support the rotational analysis. The electronic transition involved is identified to beβ ²Δ_5/2 →X ₁ ²Δ_5/2.     

On multiplication groups of relatively free quasigroups isotopic to Abelian groups

If Q is a quasigroup that is free in the class of all quasigroups which are isotopic to an Abelian group, then its multiplication group Mlt Q is a Frobenius group. Conversely, if Mlt Q is a Frobenius group, Q a quasigroup, then Q has to be isotopic to an Abelian group. If Q is, in addition, finite, then it must be a central quasigroup (a T-quasigroup).This work was supported by institutional grant MSM 113200007, and by Grant Agency of Czech Republic, grant number 201/99/0263.     

Enantioseparation of underivatised amino acids by ligand exchange capillary electrophoresis in a counter-electroosmotic mode

Enantiomer separations of underivatised amino acids were carried out by using ligand exchange capillary electrophoresis (LECE). Chiral discrimination is based on the formation of ternary complexes between copper(II), a chiral selector (L-proline or trans-4-hydroxy-L-proline) and an amino acid. All amino acids containing aromatic moieties or not were detected at 214 nm because of their interactions with copper(II). In order to reduce copper(II) adsorption onto capillary walls, we used hexadimethrine bromide to reverse the electroosmotic flow. Using this original strategy, the studied enantiomers migrated in the opposite direction of the anodic electroosmosis. After optimising the analytical conditions taking into account the chiral resolution and the detection sensitivity, we performed very satisfactory enantioseparations not only of aromatic amino acids (tryptophan, tyrosine, phenylalanine and histidine) but also of aliphatic amino acids (threonine, serine, isoleucine and valine). These enantioseparations were performed in a short analysis time at 35 °C. In order to rationalise the obtained results, we evaluated the complexation constants corresponding to the formed ternary complexes by capillary electrophoresis and we used molecular mechanics modelling.     

Experimental tests of the spectroscopic coupling for neutral oxygen

The radiation emitted from a high-current wall-stabilized arc operated in helium with some admixture of CO₂ has been studied. Intensities of fine structure components for 10 multiplets of neutral oxygen (O I) have been determined applying the emission method. On the basis of measured line intensities relative line strengths within each studied multiplet have been obtained. The results are compared with data resulting from the LS-coupling scheme and with other theoretical as well as experimental results available in literature.     

Chemical exchange in novel spirobicyclic zwitterionic Janovsky complexes using dynamic 1H NMR spectroscopy

Highly coloured Janovsky complexes have been known for over 120 years, being used in many colourimetric analytical procedures. In this present study, two novel and stable nitrocyclohexadienyl spirobicyclic, zwitterionic Janovsky anionic hydantoin σ‐complexes, rac‐1,3‐diisopropyl‐6‐nitro‐2,4‐dioxo‐1,3‐diazaspiro[4.5]deca‐6,9‐dien‐8‐ylideneazinate, ammonium internal salt (1) and 1,3‐diisopropyl‐2,4‐dioxo‐1,3‐diazaspiro[4.5]deca‐6,9‐dien‐8‐ylideneazinate, ammonium internal salt (2) have been prepared and characterised by NMR, electrospray ionization mass spectrometry (ESI‐MS) and UV/visible methods. For the p‐mononitro‐substituted complex (2), we discovered chemical exchange behaviour using 1D saturation transfer and 2D exchange spectroscopy (EXSY) ¹H NMR techniques. The coalescence temperature was determined to be 62 °C in d₃‐acetonitrile. Analysis of these data provided a Gibbs free energy of activation, ΔG ?, of + 67 kJ mole^?1, a rate constant, k, coalescence of 220 Hz and an equilibrium constant, K_eqm, of 0.98 as estimates of the exchange process in this solvent. Of the two mechanisms proposed for this fluxional behaviour, ring opening to a substituted benzene or proton exchange, a further theoretical modelling study of 1D ¹H NMR spectra was able to confirm that simple proton exchange between the two nitrogen sites of the hydantoin ring provided an accurate simulation of the observed experimental evidence. Interestingly, the o,p‐dinitro‐substituted complex (1) did not show any chemical exchange behaviour up to 150 °C in d₃‐acetonitrile (to 75 °C) and d₆‐dimethyl sulfoxide (DMSO). Molecular modelling at the MM2 level suggests that steric collisions of an N‐acyl isopropyl substituent of the hydantoin ring with the ortho‐nitro group of the spirofused cyclohexadienyl ring prevents the proposed proton exchange mechanism occurring in this case. Copyright © 2008 Crown in the right of Canada. Published by John Wiley & Sons, Ltd     

求接地导体感应电荷的一种简便方法

由一道证明题引申出一个命题,对该命题给出了证明;通过几个实例说明应用该命题可以简便地求解某些接地导体的感应电荷.     

Special features of methanol interaction with adsorbed oxygen at platinized platinum electrode: Transients of the open-circuit potential

Open-circuit potential transients are measured under the conditions of methanol interaction with the pre-adsorbed oxygen at platinized platinum electrode. The time necessary for complete removal of the adsorbed oxygen monolayer appeared being shorter by a factor of ～1.5 as compared with smooth polycrystalline platinum. The dependence of platinum surface coverage with adsorbed oxygen on the potential during its decay is found. It was shown that the reaction of methanol with the adsorbed oxygen is most slow at a high coverage (1–0.8). It is suggested that at these coverages, like the case of polycrystalline platinum, the adsorbed oxygen directly interacts with the methanol molecules from the solution. At moderate coverages (0.8–0.2), the reaction of the adsorbed oxygen with methanol at the platinized platinum is better described by the “conjugated reactions” mechanism. The specific rates of the methanol dissociative adsorption at the platinized platinum turned out to be close to those observed earlier for the polycrystalline platinum.     

从单一多位交换~(119)Sn二维交换谱求取SnCl_6~(2-)水解体系的动态交换速率常数

本文对如何从单一二维交换谱提取速率常数进行了理论分析,提出了一种近似处理方法,即把较短混合时间τ_m内在二维平面上磁化强度传递看成是单向进行的,进而导出了二维交换谱中所有峰强随τ_m变化的表达式。所得结果与Ernst的精确结果在一级近似下完全一致,在二级近似下略有不同,但将难以求解的问题转化成简单的代数方程、用这一方法对新近获得的SnCl_4·5H_2O在水溶液中的~(119)Sn二维交换谱进行了处理,得到与实验相吻合的结果,并求得了SnCI_6~(2-)水解体系的动态交换速率常数。     

Substituent Effects on Phosphate-Catalyzed Proton Exchange in Amides

The kinetics of phosphate-catalyzed proton exchange have been measured with NMR lineshape analysis for a series of amides, ureas, and carbamates. A hypothetical energy profile for transition structures of concerted phosphate catalysis ?_c and of stepwise phosphate catalysis ?₁, ?₂ is used for discussion of the substituent effects. The concerted mechanism of phosphate catalysis operates only for amides RCONHCH₃ for which the electron-donating ability of the substituent R is comparable with, or better than, that of the methyl group. We conclude that concerted phosphate catalysis is inoperative in proteins or polypeptides.