Enantioselective hydrogenation of ethyl 4 chloro 3 oxobutyrate in ionic liquid systems containing tetraethylammonium bromide, 1 butyl 3 methylimidazolium hexafluorophosphate, or 1 butyl 3 methylimidazolium trifluoromethanesulfonate in the presence of the chiral cata lyst Ru BINAP ensures a high level of asymmetric induction after at least threefold recycling of the catalyst.Key words: enantioselective hydrogenation, ethyl 4 chloro 3 oxobutyrate, ethyl 4 chloro 3 hydroxybutyrate, chiral ruthenium complexes, (R) and (S) BINAP, ionic liquid, tetraethyl ammonium bromide, recycling of the catalyst.
We have made an experimental study of the ignition of a stoichiometric hydrogen-air mixture behind the incident shock wave front in a shock tube. The ignition limits and the induction times of the mixture behind the wave front in the range of temperatures T = 550-960 K and pressures P = 0.01-1.1 MPa have been determined. Much lower values of the ignition temperature compared to the experimental results obtained in refl ected shock waves, as well as to the classical Lewis and Elbe, have been registered. The measured induction times in the above temperature and pressure ranges are in good agreement with theoretical estimates.Introduction. The ignition limits of combustible gaseous mixtures are an important characteristic of combustion and detonation processes. Most of the classical experimental works on determining the above limits in hydrogen-air mixtures were carried out under the conditions when the gaseous mixture was practically in the state of rest or moving with a low velocity [1][2][3][4]. The corresponding theoretical calculations were oriented to these experiments [5,6]. At present, in connection with the works aimed at developing hypersonic passenger airplanes burning hydrogen fuel [7], the investigation of the ignition characteristics in supersonic hydrogen-air fl ows is of interest. Therefore, the supersonic character of the gaseous mixture fl ow behind the incident shock wave in the shock tube determines the attractiveness of using this tool in pertinent experiments connected with the practical realization of the combustion process in hypersonic fl ights.Most investigations of the process of ignition of hydrogen-air mixtures in shock tubes were conducted behind refl ected waves where the gas is stationary with respect to the walls of the shock tube [8][9][10][11][12][13]. The measurand thereby was the ignition induction time of the mixture. The aim of the present work is to determine the ignition limits and the induction times of hydrogen-air mixtures in incident shock waves and compare the obtained data with the results of experiments performed behind refl ected shock waves. As the results of the investigations have shown, the value of the induction time at low-temperature ignition of the mixture is determined by the time of propagation of the combustion zone from the boundary layer heated by the supersonic fl ow into the entire volume of the shock tube.Experimental. Experiments were performed on a shock tube with an internal radius r = 28.5 mm which consisted of a high-pressure chamber of length 1 m and a low-pressure chamber of length 4.5 mm separated by a diaphragm. When the diaphragm breaks, in the low-pressure chamber the shock wave compressing and heating the investigated gas propagates. In experiments, we used devices for recording emission spectra, measuring the shock wave velocity, and recording pressure profi les in the shock wave (Fig. 1). The gas-dynamic parameters in the shock wave front were calculated for each particular experiment with the use of the "Gaseq" program from the initial p...
Experiments on isentropic compression of a substance using a high magnetic field pressure are described. Their goal is building of a zero isotherm in a multi-megabar pressures range. A method of the pressure and density determination of the compressed substance based on radiographic data obtained in the experiment is presented. The results of the experiments with solid (in initial state) protium and deuterium are presented. The densities that correspond to more than seventeen-fold compression are reached. Obtained experimental points are compared with extrapolation of a curve that is built in the experiments using anvil cells and with the results of several ab-initio calculations.
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