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71.
72.
73.
YiHU JueCHEN ZhangGaoLE ZhenChuCHEN QinGuoZHENG 《中国化学快报》2005,16(7):903-905
An efficient method is reported for the synthesis of phenacyl esters by reaction of carboxylic acids with a-bromoacetophenone promoted by potassium fluoride in ionic liquid [Bmim]PF6, the yield of the reaction is almost quantitative and the products are essentially pure. 相似文献
74.
The thermal decarboxylation of three dicarboxylic perfluoropolyether potassium salts of relatively short chain length has been investigated and the products and kinetics of the main reactions have been defined. From the rate constants and Arrhenius parameters data, the second decarboxylation appears to be quantitatively rather close to the first. 相似文献
75.
我们利用Born-Mayer-Huggins相互作用势函数对(KF)N(N=108,256,500和864)团簇进行了分子动力学(MD)模拟。为了避免周期性边界条件对相变、成核和重结晶的干扰作用,对体系采用了自由边界。基于MD模拟结果,对团簇的熔化温度、熔化焓、扩散系数、成核速率、固液界面自由能、临界核大小等进行了计算和讨论。在对(KF)864双晶团簇的热退火模拟中,观察到了固态的重结晶和晶粒的生长。经典的成核理论成功地解释了(KF)864双晶团簇的重结晶MD模拟结果。 相似文献
76.
We report a common HPLC method for the single or simultaneous determination of four calcium channel blockers (CCB), namely diltiazem (DTZ), verapamil (VER), nifedipine (NIF) and nitrendipine (NIT) and their active metabolites demetildiltiazem and deacetildiltiazem (MA and M1), norverapamil (NOR), and dehydronifedipine (DHN). DHN was first synthesised in our laboratory and different pH values of the mobil phase were subsequently prepared and tested for chromatographic separation. The detection system and the environmental light conditions were optimised. The best separations of all analytes were obtained using a C18 column and a mobile phase of methanol, 0.04 M ammonium acetate, acetonitrile and triethylamine (2:2:1:0.04 v/v). Quantitation was performed using imipramine (IMI) as the internal standard. For DTZ and its metabolites (M1 and MA), the wavelength chosen was 237 nm; for VER and its metabolite NOR, it was 210 nm; and, finally for NIF and its metabolite DHN and NIT it was 216 nm. When a simultaneous analysis was carried out the wavelength was of 230 nm. The optimum pH were 7.90 and 7.10 when the separation of NIT and DTZ or VER and NIF were carried out, respectively, and 7.90 when a simultaneous separation was carried out. The detection limit of the assay was less than 8 ng ml−1 for all compounds, with coefficients of variation less than 7% (for inter- and intra-day) over the concentration range of 1–1000 ng ml−1. The retention times were less than 11 min. When NIF or NIT were studied, it was necessary to use a sodium vapour lamp in order to avoid the photodegradation which takes place under daylight conditions. 相似文献
77.
A combined method for determination of the standard enthalpies of formation of nitroform and its salts was proposed. The enthalpies
of dissolution of nitroform and its ammonium, hydrazinium, guanidinium, and potassium salts in water were measured. The enthalpy
of combustion of hydrazinium salt of nitroform was determined by a combustion calorimetry, and its standard enthalpy of formation
was calculated. The enthalpy of formation of trinitromethyl anion in indefinitely diluted aqueous solution −24.94±0.79 kJ
mol−1, was calculated on the basic of the data obtained for enthalpies of formation and dissolution of ammonium and hydrazinium
salts of nitroform. Standard enthalpies of formation of nitroform and its salts were calculated.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2451–2454, December, 1998. 相似文献
78.
H. N. Altshuler L. P. Abramova N. V. Malyshenko G. Yu. Shkurenko E. V. Ostapova 《Russian Chemical Bulletin》2005,54(8):1978-1981
The ion-exchange equilibrium in network polymers obtained from cis-2,8,14,20-tetraphenyl-4,6,10,12,16,18,22,24-octahydroxycalix[4]arene by template synthesis on cations Na+, K+, and Ba2+ as matrices was studied. The selectivity coefficients of ion exchanges Ba2+-H+, Na+-H+, K+-H+, Na+-K+, and Na+-NH4
+ were determined. The template synthesis enhanced the affinity of the polymers to matrix-forming cations by 6–8 kJ mol−1.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1919–1922, August, 2005. 相似文献
79.
钾(Ⅰ)(苯并-15-冠-5)新型配合物的合成及性质 总被引:1,自引:0,他引:1
在非水溶剂中合成并-15-冠-5与碘化钾,硫氰化钾及苦味酸钾形成的三种新型固体配合物,并进行了有关物理,化学性质表征,结果表明,钾(Ⅰ)离子不仅易苯并-15-冠-5天成常见的1:2夹心式配合物,而且还能生成稳定的1:1型固体配合物。 相似文献
80.
James O. Alben Allan A. Croteau Frank G. Fiamingo Craig F. Hemann Virginia A. Molleran Sungjo Park Kimerly A. Powell 《Mikrochimica acta》1988,94(1-6):335-338
Biological applications of infrared spectroscopy have pressed for ever greater instrumental capabilities in terms of spectral sensitivity and quantitative exactness. Improved instrumentation has provided measurement of many vibrational modes in biological samples that previously were lost in noise. With highly optimized sampling conditions, useful measurements have been made with a peak-to-peak noise level less than 5 microabsorbance (5×10–6 absorbance), at 0.5 cm–1 resolution. However, optical and instrumental instabilities often result in sine waves that are not totally removed by the ratio of sample to reference. These often limit effective spectral sensitivity to 50 or 100 microabsorbance, peak-to-peak, and constitute a non-random noise. Non-atmospheric absorptions, especially one at 1959 cm–1 with 0.8 cm–1 band width (FWHM) are reported. The latter is due to a trace impurity in the KBr beam splitter substrate and compensator plate. Improvements in instrumentation and sampling conditions are expected to yield measurements of absorption bands as small as 50 microabsorbance with excellent signal/noise. 相似文献