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971.
Formation of higher ion aggregates mainly by hydrogen bonding in solutions of diethylcyclohexylammonium chloride (c-Hex(Et)2NHCl) has been examined by conductometry in nearly isodielectric mixed solvents: nitrobenzene-acetonitrile (35) and benzonitrile-ethanol (25) at 25°C. At lower acetonitrile content (less than ca. 10% by volume) in mixtures with nitrobenzene the salt gave minimum in the molar conductivities over the concentration range 4x10–3 to 0.12 mol-dm–3 which were explained by ion pair (MX), triple ion (M2X, MX2), and quadrupole (M2X2) formation in the solvent mixtures. The formation constants of the ion aggregates decreased with increasing content of acetonitrile. In benzonitrile-ethanol mixtures, the degrees of ion aggregate formation also decreased with increasing content of ethanol; triple ion formation could not be observed at more than 20% ethanol. 相似文献
972.
Tarek A. Salama Saad S. Elmorsy Abdel-Galel M. Khalil Mohamed A. Ismail 《Tetrahedron letters》2007,48(35):6199-6203
A general, mild and efficient protocol for the synthesis of β-amido ketone libraries was achieved utilizing tetrachlorosilane and zinc chloride in dichloromethane at ambient temperature via a one-pot, three-component condensation of various aldehydes, ketones and nitriles. 相似文献
973.
Summary The response of a flame ionisation detector (FID) to cyanogen ((CN)2) and cyanogen chloride (CNCI) has been studied. The lower limits of detection for (CN)2 and CNCl were 6×10−12 moles and 2×10−11 moles respectively. In a comparative study a thermal conductivity detector gave as its lower limit of detection for both
(CN)2 and CNCl 4×10−11 moles. Both detectors showed excellent linearity over the range 0 to 10 micromoles. The ratio of the gradients of the FID
calibrations (CN)2/CNCI were found to be approximately two suggesting the response depended on the cyanide group.
The response and stability of the FID was investigated as a function of air and hydrogen flow-rates. The response increased
with increasing air flow-rate for both (CN)2 and CNCI up to 300cm3min−1, thereafter no significant increase was observed.
On raising the hydrogen flow from 10 to 25cm3min−1 only a slight increase in the sensitivity of the FID towards both (CN)2 and CNCI was observed. At higher flow rates the response for (CN)2 increased markedly whereas at the same flow rates the response for CNCI increased only slightly. 相似文献
974.
Vinod Kumar Gupta Ajay Kumar Jain Zakariyya Ishtaiwi Heinrich Lang Gaurav Maheshwari 《Talanta》2007,73(5):803-811
PVC-based membranes of meso-tetrakis-{4-[tris-(4-allyl dimethylsilyl-phenyl)-silyl]-phenyl}porphyrin (I) and (sal)2trien (II) as electroactive material with dioctylphthalate (DOP), tri-n-butylphosphate (TBP), chloronapthalene (CN), dibutylphthalate (DBP) and dibutyl(butyl) phosphonate (DBBP) as plasticising solvent mediators have been found to act as Ni2+ selective sensor. The best performance was obtained with the sensor having a membrane of composition of I: sodium tetraphenyl borate: PVC in the ratio 5:5:150. The sensor exhibits Nernstian response in the activity range 2.5 × 10−6 to 1.0 × 10−1 M, performs satisfactorily over wide pH range (2–5.5) with a fast response time (8 s). The sensor was found to work satisfactorily in partially non-aqueous media up to 20% (v/v) content of methanol or ethanol and acetone and could be used over a period of 4 months. Potentiometric selectivity coefficients determined by matched potential method (MPM) indicate excellent selectivity for Ni2+ ions. The sensors could be used successfully in the estimation of nickel in different brand of chocolates and also as an indicator electrode in potentiometric titration. 相似文献
975.
酰氨基硫脲及其相关化合物通常具有广泛的生物活性 ,如抗菌[1~ 3] ,抑制神经紧张[4] ,治疗血糖过低[5] ,植物生长调节[6~ 9] 等。迄今为止 ,鲜有关于双 (1 ,4 二酰基氨基硫脲 )合成的报道。为了考查该类化合物的生物活性 ,我们设计合成了一系列双 (1 ,4 二酰基氨基硫脲 )化合物 ,以下图所示的两条合成路线合成了该类化合物 :二酰氯 (1 )、异硫腈酸酰酯 (2 )等中间体可不经进一步纯化直接用于下一步反应。所生成的产物 3a 3f、3′d 3′g经DMF H2 O EtOH重结晶 ,产率达 81 %~ 98%。在合成化合物 (1 )时 ,对于一些用SOCl2 … 相似文献
976.
G. Barone P. Del Vecchio D. Fessas C. Giancola G. Graziano A. Riccio 《Journal of Thermal Analysis and Calorimetry》1994,41(6):1357-1370
It is presented a study concerning the influence of guanidinium chloride (GuHCl) and urea on thermal stability of Bovine Pancreatic Ribonuclease A (RNAase A) at differentpH values. As expected, at increasing the denaturant concentration, the protein thermostability decreases. This is shown by a decrease of both the thermodynamic parameters, temperature and heat effect, characterising the denaturation process. In order to analyse the calorimetric curves we adopt a statistical thermodynamic approach. The individual one-dimensional DSC profiles have been expanded into another dimension by varying the GuHCl concentration, so that a heat capacity surface is defined for eachpH. By means of the ICARUS program, developed in our laboratory, we accomplish a two dimensional deconvolution of the experimental data linking the binding equilibrium to the denaturation process. This analysis provides a well founded and complete statistical thermodynamic characterisation of denaturation process of RNAase A in the presence of GuHCl and allows to calculate the thermodynamic parameters associated to the binding of denaturant molecule. 相似文献
977.
光原锰(Ⅲ)卟啉二甲酯与有机碱配位还原反应研究 总被引:2,自引:0,他引:2
实验表明,Mn(Ⅲ)卟啉对理解血红蛋白的催化反应很有意义。Mn(Ⅲ)卟啉突出的性质是配位还原性,尤其与有机碱的反应。等研究了四苯基卟啉锰(Ⅲ)(TPPMn(Ⅲ)Cl)与有机碱的配位还原反应。本文部分作者曾研究过(β-硝基)四苯基卟啉锰(Ⅲ),((β-NO_2)TPP Mn(Ⅲ)Cl)、四(对硝基)苯基卟啉锰(Ⅲ)(TNPPMn(Ⅲ)Cl)和邻(二 相似文献
978.
T. Ito Y. Yoshioka T. Sonoda Y. Yoshihashi E. Yonemochi K. Terada 《Journal of Thermal Analysis and Calorimetry》2006,85(3):731-739
Glass
ampoule breakage during the freeze-drying process was prevented by the addition
of sodium chloride to the formulation of lyophilization products of sodium
thiopental. In order to clarify the ampoule breakage prevention mechanism,
the physicochemical behavior of the freeze-drying process was monitored by
simultaneous XRD-DSC measurements and thermal mechanical analysis (TMA). During
the freezing process of formulated solution, the smaller heat of fusion of
crystallized ice with the addition of sodium chloride was observed in comparison
to that without sodium chloride. Although a greater amorphous portion remained,
a higher crystal habit of hexagonal ice was reproducibly observed in the XRD
patterns with the addition of sodium chloride during the freezing process.
In the measurement of TMA, the scattering of the thermal expansion rate of
formulated solution was significantly reduced by the addition of sodium chloride.
These observations indicated that the addition of sodium chloride minimized
the scattering of the thermal expansion rate and might be a cause for the
inhibition of glass ampoule breakage during the freeze-drying process. 相似文献
979.
D. Góralczyk 《Colloid and polymer science》1994,272(2):204-210
The effect of sodium chloride concentration on the simultaneous adsorption of dodecylpyridinium chloride (R12PyCl) and sodium octylsulfonate (R8SO3Na) on the free surface of their aqueous solutions has been examined. The composition of mixed films adsorbed from equimolar solutions has been determined on the basis of the Gibbs adsorption equation as well as by using the regular solution model. It has been stated that this composition is dependent on the surface tension value (the degree of the surface coverage) as well as on the concentration of added inorganic electrolyte. The same factors influence the value of the interaction parameter , which negative values indicate a strong attraction between the components in the mixed monolayer. 相似文献
980.
Samir Kumar Mandal 《Tetrahedron letters》2005,46(36):6115-6117
Free radical-promoted conjugate addition of activated bromo compounds to α,β-unsaturated ketones and reactive α,β-unsaturated esters has been described using titanocene(III) chloride (Cp2TiCl) as the radical initiator. Cp2TiCl was prepared in situ from commercially available Cp2TiCl2 and activated zinc dust in THF. 相似文献