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71.
Jozsef Béres Wesley G. Bentrude Jeno Tomasz Alan E. Sopchik 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract An investigation of the effects of changing the nature of X, nitrogen base (B), and amino substituent (R2N) on the equilibrium 1?2 was carried out. The influence of the above structural changes on the time-averaged coupling constants JAP and JBP, determined at 300 MHz, were used to follow changes in Keq. With constant R2N, small effects from variation of X and B were found. A large range in Keq arose from changes in the steric size of R2N. These results will be related to the question of the ease of chair to twist interconversion of the phosphate ring essential to the biological activities of the naturally occurring diesters, cAMP and cGMP. 相似文献
72.
Bogdan Boduszek Tomasz Olszewski Waldemar Goldeman Magdalena Konieczna 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):787-795
The synthesis of a series of new pyridine aminomethylphosphinic acids is described. These compounds were obtained in the reaction of the corresponding pyridine aldehydes with primary amines and with ethyl phenylphosphinate, or methylphosphinate, in the presence of bromotrimethylsilane. In aqueous, strong acid solutions, pyridine aminophosphinic acids were split, forming the phenyl-, or methylphosphonic, acid and the corresponding secondary pyridyl-alkylamines. The kinetics of some observed cleavages were measured, and a mechanism of the cleavage has been proposed. 相似文献
73.
Monika Michel Luke Chimuka Tomasz Kowalkowski Ewa M. Cukrowska Bogusław Buszewski 《Journal of separation science》2013,36(5):986-991
An artificial neural network model of supported liquid membrane extraction process with a stagnant acceptor phase is proposed. Triazine herbicides and phenolic compounds were used as model compounds. The model is able to predict the compound extraction efficiency within the same family based on the octanol–water partition coefficient, water solubility, molecular mass and ionisation constant of the compound. The network uses the back‐propagation algorithm for evaluating the connection strengths representing the correlations between inputs (octanol–water partition coefficients logP, acid dissociation constant pKa, water solubility and molecular weight) and outputs (extraction efficiency in dihexyl ether and undecane as organic solvents). The model predicted results in good agreement with the experimental data and the average deviations for all the cases are found to be smaller than ±3%. Moreover, standard statistical methods were applied for exploration of relationships between studied parameters. 相似文献
74.
Pawel Mierczynski Waldemar Maniukiewicz Tomasz P. Maniecki 《Central European Journal of Chemistry》2013,11(6):912-919
The activity of monometallic Pd, Ru, Ni and Cu catalysts supported on spinel ZnAl2O4 for water gas shift reaction (WGS) was investigated. The physicochemical properties of each catalyst was studied by XRD, TPR, BET and chemisorption methods. The highest activity was obtained for Cu/ZnAl2O4 among the catalysts tested. The activation process carried out in a reducing atmosphere 5%H2-95%Ar in the case of Cu/ZnAl2O4 system lead to the catalytic activity improvement. In the case of copper catalysts, the water gas shift reaction proceeded by the redox surface mechanism between Cu0/Cu+. The PdZn alloy formation after reduction at 350°C was shown. 相似文献
75.
The efficient synthesis of 2-phenylethynyl- or 2-phenylthioethynyl-2-substituted phenylacetonitriles 4 and 5 from nitriles 3 and substituted dichloroethenes 1 or 2, respectively, in the presence of 50% aqueous sodium hydroxide and tetrabutylammonium hydrogen sulphate (TBAHS) as a catalyst (phase-transfer catalysis, PTC), has been accomplished. 相似文献
76.
Jarosław Sławiński Aneta Pogorzelska Beata Żołnowska Tomasz Laskowski Paweł Sowiński 《Tetrahedron》2013
3-Amino-1,1-dioxopyrido[4,3-e]-1,4,2-dithiazine has been synthesized and applied to the synthesis of 3-amino-2-(4-thioxo-1,4-dihydropyridin-3-ylsulfonyl)guanidine. The reaction of the aminoguanidine with the appropriate 1,2-diarylethane-1,2-diones afforded 2,3-diaryl-9,9-dioxo-1H-9-thia-1,4,4a,7,10-pentaazaphenanthrene-2-ol derivatives. The structure of these compounds, which represent a novel heterocyclic ring system, was confirmed on the basis of elemental analysis and spectroscopic data including COSY, NOESY, ROESY, HSQC, and HMBC. 相似文献
77.
The stereoselective synthesis of two epimeric penta-hydroxylated indolizidines was accomplished from 2,3:5,6-di-O-isopropylidene-α-d-mannofuranose and N-(2-methylpent-4-en-2-yl)hydroxylamine. The transformation of these substrates into the corresponding 7-oxa-1-azabicyclo[2.2.1]heptane by the intramolecular 1,3-dipolar cycloaddition was the key step of the synthesis. The adduct was transformed into the tricyclic ammonium salt by intramolecular N-alkylation. The tricyclic ammonium salt was converted to the target compounds by: (route 1) the catalytic hydrogenation; or (route 2) the reaction with sodium azide, followed by the enantioselective reduction of the resulting indolizidinone. 相似文献
78.
Langmuir and Langmuir-Blodgett (LB) films of a perylene-like compound and its binary mixtures with 4-octyl-4'-cyanobiphenyl (8CB) and 4-pentyl-4"-cyano-p-terphenyl (5CT) have been studied. On the basis of the surface pressure-area isotherms, the molecular organization on the air-water interface has been estimated. Information about the miscibility or the phase separation of components in the binary mixtures has been obtained. The spectroscopic study of the LB films has allowed conclusions to be drawn about the arrangement of the molecules on the quartz slides. The fluorescence spectra of the LB films of the perylene-like compound have revealed the formation of self-aggregates. 相似文献
79.
Langmuir films of binary mixtures of the following liquid crystal materials: 4-octyl-4′-cyanobiphenyl (8CB) or 4-pentyl-4″-cyano-p-terphenyl (5CT) with 4-(trans-4'-octylcyclohexyl)isothiocyanatobenzene (8CHBT), trans-4-octyl(4′-cyanophenyl)cyclohexane (8PCH) or 4-octyl4′-isothiocyanatobiphenyl (8BT) were investigated. Surface pressure-mean molecular area isotherms were recorded at various mixture compositions. It was found that only liquid crystal materials for which the molecules have a terminal -CN group are able to form a stable monolayer at the air-water interface. Moreover, information about the miscibility or the phase separation of the two components in the mixures was obtained by using the excess area criterion and surface phase rules. 相似文献
80.
Valentina Ljubomirova Rumyana Djingova Johannes T. van Elteren Marjan Veber Tomasz Kowalkowski Boguslaw Buszewski 《International journal of environmental analytical chemistry》2013,93(7):499-512
A sequential extraction procedure (three-step), proposed by the Standards, Measurements and Testing Programme (formerly BCR) of the European Union, was applied to street dust and spiked soil samples for the determination of PGEs. Analyses were carried out using inductively coupled plasma-mass spectrometry (ICP-MS). The results indicate that up to 5% from Pt, 70% from Pd and 14% from Rh are in mobile forms in street dust. The results for the soil samples spiked with crushed catalytic converter are significantly lower indicating that PGEs are oxidised more efficiently in natural conditions. Additionally Pt and Pd bound to humic acids were investigated. 相似文献