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131.
Reviriego F Navarro P García-España E Albelda MT Frías JC Domènech A Yunta MJ Costa R Ortí E 《Organic letters》2008,10(22):5099-5102
The synthesis and steady-state fluorescence studies on the interaction with AMPH, METH, MDMA, and DA of two diazatetraester pyrazole crowns containing appended N-(9H-fluoren-9-yl) and N-(naphth-2-ylmethyl) functions, in a water/ethanol 70:30 mixture at physiological pH, are described. 相似文献
132.
Monteiro MJ Bazito FF Siqueira LJ Ribeiro MC Torresi RM 《The journal of physical chemistry. B》2008,112(7):2102-2109
Lithium salt solutions of Li(CF3SO2)2N, LiTFSI, in a room-temperature ionic liquid (RTIL), 1-butyl-2,3-dimethyl-imidazolium cation, BMMI, and the (CF3SO2)2N(-), bis(trifluoromethanesulfonyl)imide anion, [BMMI][TFSI], were prepared in different concentrations. Thermal properties, density, viscosity, ionic conductivity, and self-diffusion coefficients were determined at different temperatures for pure [BMMI][TFSI] and the lithium solutions. Raman spectroscopy measurements and computer simulations were also carried out in order to understand the microscopic origin of the observed changes in transport coefficients. Slopes of Walden plots for conductivity and fluidity, and the ratio between the actual conductivity and the Nernst-Einstein estimate for conductivity, decrease with increasing LiTFSI content. All of these studies indicated the formation of aggregates of different chemical nature, as it is corroborated by the Raman spectra. In addition, molecular dynamics (MD) simulations showed that the coordination of Li+ by oxygen atoms of TFSI anions changes with Li+ concentration producing a remarkable change of the RTIL structure with a concomitant reduction of diffusion coefficients of all species in the solutions. 相似文献
133.
Rodrigo S. Corrêa Felipe T. Martins Javier Ellena Marcelo H. dos Santos Antonio C. Doriguetto 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(7):o395-o397
The asymmetric unit of the title compound, C6H9N2OS2+·HSO4−·H2O, contains a heterocyclic cation, a hydrogen sulfate anion and a water molecule. There are strong hydrogen bonds between the hydrogen sulfate anions and water molecules, forming an infinite chain along the [010] direction, from which the cations are pendent. The steric, electronic and geometric features are compared with those of similar compounds. In this way, structural relationships are stated in terms of the influence of the sulfate group on the protonation of the heterocycle and on the tautomeric equilibrium in the solid state. 相似文献
134.
A. B. Siqueira C. T. Carvalho E. Y. Ionashiro G. Bannach E. C. Rodrigues M. Ionashiro 《Journal of Thermal Analysis and Calorimetry》2008,92(3):945-951
Solid-state Ln(L)3 compounds, where Ln stands for trivalent Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y and L is 2-methoxybenzoate have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential
scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy and complexometry were used to characterize
and to study the thermal behaviour of these compounds. The results provided information on the composition, dehydration, coordination
mode, structure, thermal behaviour and thermal decomposition. 相似文献
135.
Today's demand for precisely predicting chemical reactions from first principles requires research to go beyond Gibbs' free energy diagrams and consider other effects such as concentrations and quantum tunneling. The present work introduces overreact, a novel Python package for propagating chemical reactions over time using data from computational chemistry only. The overreact code infers all differential equations and parameters from a simple input that consists of a set of chemical equations and quantum chemistry package outputs for each chemical species. We evaluate some applications from the literature: gas-phase eclipsed-staggered isomerization of ethane, gas-phase umbrella inversion of ammonia, gas-phase degradation of methane by chlorine radical, and three solvation-phase reactions. Furthermore, we comment on a simple solvation-phase acid–base equilibrium. We show how it is possible to achieve reaction profiles and information matching experiments. 相似文献
136.
Dr. Javier F. Reynes Dr. Felipe García 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202215094
Several mechanochemically heated processes have been published in recent years. However, precise control over the mechanochemical catalysed coupling reactions remained elusive. A recent report from Leitch, Browne and co-workers demonstrated how a programmable jar heater manifold delivers an efficient methodology for the Suzuki–Miyaura-type cross coupling reaction of aryl sulfamates and aryl boronic acid species. This methodology can be readily upscaled 200-fold using twin-screw extrusion methodologies. 相似文献
137.
Derogis PB Martins FT de Souza TC de C Moreira ME Souza Filho JD Doriguetto AC de Souza KR Veloso MP Dos Santos MH 《Magnetic resonance in chemistry : MRC》2008,46(3):278-282
This article reports the structural elucidation by IR, UV and MS spectroscopic data along with 1H and 13C NMR chemical shift assignments of two benzophenones isolated from the fruit pericarp of Garcinia brasiliensis Mart. (Clusiaceae): garciniaphenone, (1R,5S,7S)-3-benzoyl-4-hydroxy-6,6-dimethyl-5,7-di(3-methyl-2-butenyl)bicyclo[3.3.1]non-3-ene-2,9-dione, a novel triprenylated benzophenone; and 7-epi-clusianone, a tetraprenylated benzophenone that has already been extracted from another species of the same family. Furthermore, the keto-enol tautomeric equilibrium at solution-state was described for these compounds by 1D and 2D NMR spectral methods and one attempt to rationalize the different ratios between the noted tautomers was based on stereochemical features. 相似文献
138.
Dörr FA Tomaz JC Lopes NP Pinto E 《Rapid communications in mass spectrometry : RCM》2008,22(13):2015-2020
Cylindrospermopsin (CYN) belongs to a group of toxins produced by several strains of freshwater cyanobacteria. It is a compact zwitterionic molecule composed of a uracil section and a tricyclic guanidinium portion with a primarily hepatotoxic effect. Using low multi-stage and high-resolution mass spectrometry, the gas-phase reactions of this toxin have been investigated. Our data show that collision-induced dissociation (CID) spectra of CYN are dominated by neutral losses, and three major initial fragmentation pathways are clearly distinguishable. Interestingly, comparative analysis of protonated and cationizated molecules showed a significant difference in the balance of the SO3 and terminal ring elimination. These data indicate that the differential ion mobility of H+, Li+, Na+ and K+ leads to different fragmentation pathways, giving rise to mass spectra with different profiles. 相似文献
139.
A high performance liquid chromatography (HPLC) method for the detection and quantitation of acetaldehyde, glyceraldehyde, pyruvic acid, 2-ketoglutaric acid, and formaldehyde in wine, based on the formation of the 2,4-dinitrophenylhydrazones, is presented. These carbonyl compounds often result from the chemical oxidation of major wine components, and are known to affect flavor and color stability. Their analysis in wine is complicated due to their instability and their tendency to react reversibly with bisulfite to form α-hydroxysulfonates. Published methods that break down the sulfonates for the quantitation of total carbonyls in wine involve alkaline hydrolysis of sulfite-bound carbonyls, but we show, for the first time, that this alkaline treatment step significantly increases the concentration of carbonyls during analysis. A solution based on oxygen exclusion is described. The technique offers good specificity, reproducibility (%RSD 0.45-10.6), and limits of detection (1.29-7.53 μg L−1). The method was successfully used to monitor concentration changes of these compounds in both white and red wines. 相似文献
140.
Gándara F Medina ME Snejko N Gómez-Lor B Iglesias M Gutiérrez-Puebla E Monge MA 《Inorganic chemistry》2008,47(15):6791-6795
[C 6H 10(NH 2) 2Ge 3O 6] ICMM9 is a two-dimensional germanate in which the metallic atoms are covalently bonded to chelating diamines. Its layered structure having some similitude with that of the pyroxene mineral, presents a totally new topology with two 4-c nodes. The solvothermal synthesis reaction allows the separation in situ of the two 1,2-diaminocyclohexane isomers by selective coordination of the trans isomer to octahedral Ge atoms of the ICMM9 framework. This material behaves as an active and selective heterogeneous acid-base bifunctional catalyst. 相似文献