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81.
Tadeusz Micha?owski Agustin G. Asuero Maja Ponikvar-Svet Marcin Toporek Andrzej Pietrzyk Maciej Rymanowski 《Journal of solution chemistry》2012,41(7):1224-1239
The paper compares two approaches to the simulated argentometric titration of cyanide with the use of the modified Liebig?CDenigès (L-D) method, carried out according to GATES and applied with (1) classical and (2) pH-static titrations. Both approaches are discussed thoroughly and the results obtained from calculations are presented graphically. The calculations are performed with the use of an iterative computer program, based on charge and concentration balances and expressions for equilibrium constants, providing all physicochemical knowledge of the dynamic system in question. This way, physicochemical knowledge on complex electrolytic systems can be gained during the analytical procedure, i.e., the physicochemical and analytical knowledge are interrelated. The simulations follow the analytical procedures applied in experimental titrations and so provide an example of searching for the best a priori conditions for the quantitative analysis of cyanide. The computer program for pH-static titrations (described in this paper) enables one to carry out the simulation procedures with different preliminary data (concentrations, volumes). 相似文献
82.
83.
Mario Komar Tatjana Gazivoda Kraljevi Igor Jerkovi Maja Molnar 《Molecules (Basel, Switzerland)》2022,27(2)
In this study, deep eutectic solvents (DESs) were used as green and eco-friendly media for the synthesis of substituted 2-mercaptoquinazolin-4(3H)-ones from different anthranilic acids and aliphatic or aromatic isothiocyanates. A model reaction on anthranilic acid and phenyl isothiocyanate was performed in 20 choline chloride-based DESs at 80 °C to find the best solvent. Based on the product yield, choline chloride:urea (1:2) DES was found to be the most effective, while DESs acted both as solvents and catalysts. Desired compounds were prepared with moderate to good yields using stirring, microwave-assisted, and ultrasound-assisted synthesis. Significantly, higher yields were obtained with mixing and ultrasonication (16–76%), while microwave-induced synthesis showed lower effectiveness (13–49%). The specific contribution of this research is the use of DESs in combination with the above-mentioned green techniques for the synthesis of a wide range of derivatives. The structures of the synthesized compounds were confirmed by 1H and 13C NMR spectroscopy. 相似文献
84.
Božidar Čobeljić Andrej Pevec Stepan Stepanović Milica R. Milenković Iztok Turel Maja Gruden Dušanka Radanović Katarina Anđelković 《Structural chemistry》2018,29(6):1797-1806
The isothiocyanato Zn(II) complex (1) and mixed isothiocyanato/thiocyanato Cd(II) complex (2) with the condensation product of 2-acetylpyridine and trimethylammoniumacetohydrazide chloride (Girard’s T reagent) (HLCl) were investigated both experimentally and theoretically. The crystal structures of both complexes showed tridentate N2O coordination of hydrazine ligand. In complex 1 square-pyramidal coordination surrounding of Zn(II) consists of deprotonated hydrazone ligand and two isothiocyanato ligands, while in octahedral Cd(II) complex ligand is coordinated without deprotonation as a positively charged species and coordination geometry is completed with two N-coordinated and one S-coordinated NCS? anions. NMR spectroscopy and molar conductivity results for Cd(II) and Zn(II) complexes indicated their instability in solution. DFT calculations were performed to explain coordination preference and stability of complexes 1 and 2 in solid state and in solution. The obtained Cd(II) complex is the first reported mononuclear pseudohalide/halide Cd(II) complex with quinoline-/pyridine-based hydrazone ligands possessing octahedral geometry in solid state. In this complex, H-bonding has significant impact on coordination number and supramolecular assembly in solid state. 相似文献
85.
Let R be a ring with involution *. We consider R as a ring equipped with a new product r s = rs + sr*. The relationship between (ordinary) ideals of R and right ideals of R with respect to the product is studied.AMS Subject Classification (2000): 16W10, 16D25 相似文献
86.
Aleksandra S.Kosti 《Algebra Colloquium》2021,28(4):625-634
Let R be an associative unital ring and not necessarily commutative.We analyze conditions under which every n × n matrix A over R is expressible as a sum A =E1 +…+ Es + N of (commuting) idempotent matrices Ei and a nilpotent matrix N. 相似文献
87.
Structural Chemistry - The newly measured ionization potential of atomic astatine is discussed and compared with that of the recently determined value for polonium and for the other atomic... 相似文献
88.
The elementary steps of the anodic oxidation of ethanol on Pt in sulfuric acid are visualized with differential electrochemical mass spectroscopy (DEMS) by means of deuterium and 18O labelling. It turns out that: (i) ethanol is oxidized directly to acetaldehyde by the cleavage of one hydrogen of the α-C-atom and the hydroxyl hydrogen; (ii) a strongly bound intermediate is formed in parallel; (iii) the intermediate is oxidized at 0.7 V to give two CO2 molecules, one originating from the alcoholic group and still containing the alcoholic O, the other from the methyl group; (iv) CC bond splitting seems to occur during the oxidation of the adsorbate only. 相似文献
89.
JPC – Journal of Planar Chromatography – Modern TLC - Experiments and calculations show the importance of analytical management to reliable analytical results. A method with a... 相似文献
90.