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排序方式: 共有101条查询结果,搜索用时 15 毫秒
1.
The relative permittivity of 1,2-dimethoxyethane and N,N-dimethylformamide mixtures from −10 to 40°C
Gianni Goldoni Luigi Marcheselli Andrea Marchetti Lorenzo Tassi Giuseppe Tosi 《Journal of solution chemistry》1992,21(9):953-962
Binary solutions of N,N-dimethylformamide and 1,2-dimethoxyethane have been investigated by means of dielectric measurements at temperatures ranging from –10 to +40°C, and for nine mixtures covering the whole miscibility field expressed by the mole fraction of one component (0X11). The experimental data were used to study the dependence of on T and X1, of the type = (T), = (X1), and = (T,X1). Further, the excess mixing function E has been evaluated in order to identify particular patterns of interaction between unlike molecules and any other factor that could modify such patterns. The minimum in the E vs. composition plots suggests the formation of an adduct of stoichiometric ratio DMFDME=11 at all the investigated temperatures. 相似文献
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Fabrizio Casarini Luigi Marcheselli Andrea Marchetti Lorenzo Tassi Giuseppe Tosi 《Journal of solution chemistry》1993,22(10):895-905
The relative permittivities for the ternary 1,2-ethanediol (component 1) + 2-methoxyethanol (2) + water (3) solvent system have been measured for 66 mixtures covering the whole mole fraction composition 0X1/X2/X3 1 range at –10, –5 and 0 °C. The experimental data were used to test some empirical relations stating the dependence of = (X1, X2, X3). A comparison between the calculated and experimental data show that these equations can be usefully employed to predict values in correspondence of the experimental data gaps. 相似文献
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Maria G. Bettoli Lorenzo Cantelli Damiano Quarin Marzia Ravanelli Laura Tositti Ottavio Tubertini 《International journal of environmental analytical chemistry》2013,93(3-4):321-330
Abstract 210Pb is widely used to determine accumulation rates in order to obtain a time scale in environmental samples. The most accurate method uses the determination of 210Pb via its grand-daughter 210Po by alpha spectrometry. Unfortunately this method requires a complex wet-chemistry procedure to achieve the separation of 210Po from its matrix. In this work a simplified procedure for the chemical separation of 210Po is proposed and applied to three marine sediment cores and a 10 m snow core collected in Antarctica. The calculated sedimentation rates for marine sediments range from 0.053 to 0.071 cm y?1. The mean annual accumulation rate for the snow is 16.6 cm y?1 w.e. A comparison with literature data in the same region is given. 相似文献
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Dr. Marzia Dell'Aera Dr. Filippo Maria Perna Dr. Paola Vitale Dr. Angela Altomare Prof. Alessandro Palmieri Dr. Lewis C. H. Maddock Leonie J. Bole Dr. Alan R. Kennedy Prof. Eva Hevia Prof. Vito Capriati 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(40):8742-8748
We report the first transition metal catalyst- and ligand-free conjugate addition of lithium tetraorganozincates (R4ZnLi2) to nitroolefins. Displaying enhanced nucleophilicity combined with unique chemoselectivity and functional group tolerance, homoleptic aliphatic and aromatic R4ZnLi2 provide access to valuable nitroalkanes in up to 98 % yield under mild conditions (0 °C) and short reaction time (30 min). This is particularly remarkable when employing β-nitroacrylates and β-nitroenones, where despite the presence of other electrophilic groups, selective 1,4 addition to the C=C is preferred. Structural and spectroscopic studies confirmed the formation of tetraorganozincate species in solution, the nature of which has been a long debated issue, and allowed to unveil the key role played by donor additives on the aggregation and structure of these reagents. Thus, while chelating N,N,N’,N’-tetramethylethylenediamine (TMEDA) and (R,R)-N,N,N’,N’-tetramethyl-1,2-diaminocyclohexane (TMCDA) favour the formation of contacted-ion pair zincates, macrocyclic Lewis donor 12-crown-4 triggers an immediate disproportionation process of Et4ZnLi2 into equimolar amounts of solvent-separated Et3ZnLi and EtLi. 相似文献
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Dr. Alessandro Presentato Dr. Antonino Scurria Dr. Lorenzo Albanese Dr. Claudia Lino Dr. Marzia Sciortino Dr. Mario Pagliaro Dr. Federica Zabini Dr. Francesco Meneguzzo Prof. Rosa Alduina Dr. Domenico Nuzzo Dr. Rosaria Ciriminna 《ChemistryOpen》2020,9(5):628-630
Pectin extracted via hydrodynamic cavitation in water only from waste lemon peel and further isolated via freeze drying displays significant antibacterial activity against Staphylococcus aureus, a Gram positive pathogen which easily contaminates food. The antibacterial effect of the new IntegroPectin is largely superior to that of commercial citrus pectin, opening the way to advanced applications of a new bioproduct now obtainable in large amounts and at low cost from citrus juice industry's waste. 相似文献
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A four step synthesis of 4(S)-oxazolidineacetic acid, 2-oxo benzyl ester (D-Oxac-OBn) from L-Asp-OH in 45% overall yield is reported. The formation of by-products is completely avoided, by microwave irradiation and by the use of caesium carbonate as base. Moreover the synthesis and IR and 1H NMR conformational analysis of the tetramers Boc-L-Val-D-Oxac-L-Ala-OBn and Boc-L-Val-D-Oxac-Aib-L-Ala-OBn in solution is reported. 相似文献
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