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91.
Magdalena Kurdziel Elżbieta Szczepaniec-Cieciak Monika Watorczyk Barbara Dabrowska 《Journal of solution chemistry》2004,33(5):453-464
The solubility of solid 2-methyl-1,3-butadiene (isoprene) in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K has been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in the solute. The experimental value of the mole fraction solubility of solid isoprene in liquid argon at 87.3 K is (1.41 ± 0.27) × 10–6 and (1.56 ± 0.36) × 10–7 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbon in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l
12 were also calculated. At 90.0 K liquid argon is a better solvent for isoprene than is liquid nitrogen. The experimental values of the solubilities of isoprene in liquid argon and nitrogen were compared with results obtained for selected unsaturated and aromatic hydrocarbons. 相似文献
92.
Magdalena Kurdziel Elżbieta Szczepaniec-Cięciak Barbara Dąbrowska Wojciech Nitek Katarzyna Paliś Edyta Ślusarska 《Journal of solution chemistry》2003,32(7):601-615
The solubilities of solid 2,3-dimethylbutane and cyclopentene in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K have been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in solutes. The experimental value of the mole fraction solubility of solid 2,3-dimethyl-butane in liquid argon at 87.3 K is (8.26 ± 1.60) × 10–6 and (2.77 ± 0.94) × 10–8 in liquid nitrogen at 77.4 K. The experimental value of the mole fraction solubility of solid cyclopentene in liquid argon at 87.3 K is (5.11 ± 0.44) × 10–6 and (4.60 ± 0.76) × 10–8 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbons in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l
12 were also calculated. At 90.0 K liquid argon is a better solvent for investigated solid hydrocarbons than is liquid nitrogen. 相似文献
93.
Fowler CJ Sessler JL Lynch VM Waluk J Gebauer A Lex J Heger A Zuniga-Y-Rivero F Vogel E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(15):3485-3496
Porphyrin (P), porphycene (Pc), corrphycene (Cn), and hemiporphycene (Hpc) represent a series of well defined "4-N in" constitutional porphyrin isomers. These isomers, in the form of their octaethyl derivatives, represent a congruent set of porphyrinoids whose properties can be compared. In this study we report how variations in electronic structure and nitrogen-core size in the free-base forms of these four systems are reflected in the properties of their corresponding metal complexes. Specifically, the effects that these differences have on the axial ligation properties of the Zn(II), Mg(II), Ni(II), and Co(II) complexes of P, Pc, Cn, and Hpc in toluene using pyridine as the axial ligand are detailed. Also reported are the relative stabilities of these complexes under acidic conditions. It is shown that for the zinc, magnesium, and cobalt complexes, there are distinct differences in the ability to maintain four-, five-, or six-coordinate geometries in the presence of similar concentrations of pyridine. By contrast, no apparent differences in axial ligand binding affinity are seen for the four nickel complexes. Little difference in stability was likewise seen when these same complexes were subject to acid-mediated demetallation, with all four falling into stability class II, according to the accepted porphyrin stability ranking system. High stabilities were also seen in the case of the cobalt complexes, with the Pc and Cn complexes being of stability class III and the P and Hpc derivatives falling into stability class II. The Zn(II) and Mg(II) complexes were all far less stable than the corresponding Ni(II) and Co(II) complexes. In this case, semiquantitative analyses of the rate of acid-induced decomposition revealed the following stability sequence P>Cn>Hpc>Pc for both the Zn(II) and Mg(II) complexes. Single-crystal X-ray diffraction structures were solved for the Zn(II), Mg(II), and Ni(II) complexes of the octaethyl derivatives of Hpc, Cn, and Pc as well as a Co(II) octamethylcorrphycene and are reported as part of this study. These solid-state structures confirm four-coordinate species for the Ni(II) complexes, four- and five-coordinate species for the Mg(II) and Zn(II) complexes, and a six-coordinate species for the lone Co(II) complex. 相似文献
94.
Sergey I. Vdovenko Igor I. Gerus Natalia V. Lutenko Valery P. Kukhar Jacek Wjcik 《Journal of Molecular Structure》2007,840(1-3):125-132
Spatial structure of six β-substituted enones, with common structure R1O–CR2CH–COCF3, were R1 = C2H5, R2 = H (ETBO); R1 = R2 = CH3 (TMPO); R1 = C2H5, R2 = C6H5 (ETPO); R1 = C2H5, R2 = 4- O2NC6H4 (ETNO); R1 = C2H5, R2 = C(CH3)3 (ETDO) were investigated by 1H and 19F NMR, infrared spectroscopy and AM1 calculations. NMR spectra revealed that enones (MBO), (ETBO) and (TMPO) are exclusively (3E) isomers, whereas in (ETPO), (ETNO) and especially in (ETDO) the percentage of (3Z) isomers is significant and depends on the nature of solvents. Conformational behaviour of studied enones are determined by the rotation around of CC double bond, C–C and C–O single bonds (correspondingly trifluoroacetyl and alkoxy groups), and (EZZ) conformer being the most stable in all cases. IR spectra revealed that with the exception of (ETDO) (EZZ) conformer is most populated in all cases. Bulky substituents like phenyl or tert-butyl group at β-position of enone result in the equilibrium mainly between (EZZ) and (ZZZ) forms, whereas β-hydrogen and β-methyl substituents determine the equilibrium between (EZZ) and (EEZ) or (EZE) conformers. 相似文献
95.
Zinc(II) and mercury(II) complexes were prepared by reacting isatin-3-thiosemicarbazone (ISTSCH) with zinc(II) acetate or mercury(II) bromide. The complexes were characterized by IR, Raman, diffuse reflectance, 1H and 13C NMR spectra and elemental analysis. Tetrahedral structures for Zn(ISTSC)2 and Hg(ISTSCH)Br2 are suggested. 相似文献
96.
Wojakowska A. Krzyżak E. Wojakowski A. 《Journal of Thermal Analysis and Calorimetry》2001,65(2):491-495
The phase diagram for the RbBr–CuBr system has been determined. In the system two intermediate compounds are formed: RbCu2Br3, melting congruently at 537 K and Rb3CuBr4, melting incongruently at 544 K. The coordinates of the two eutectic points are: 501 K, 54 mole% CuBr and 522 K, 74 mole%
CuBr.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
97.
Five chemical compounds, CuMoO4, Cu3Mo2O9, Cu2Mo3O10, Cu6Mo4O15, and Cu4?x Mo3O12 (0.10 ? x ? 0.40), were identified in the system Cu2OCuOMoO3 and characterized by DTA, X-ray powder patterns, ir spectra, and magnetic properties. Cupric molybdates CuMoO4 and Cu3Mo2O9 are stable in air up to 820 and 855°C, respectively, melting at these temperatures with simultaneous decomposition (oxygen loss). Congruent mp of cuprous molybdates Cu2Mo3O10 and Cu6Mo4O15, in argon, are 532 and 466°C, respectively. Nonstoichiometric phase Cu4?x Mo3O12 = Cu2+3Cu01?xMo6+3O12, melts in argon between 630 and 650°C depending on the value of x and at 525–530°C undergoes polymorphic transformation. Areas of coexistence of the above-mentioned phases are determined. The μeff of Cu2+ ions and θ values are: 1.80 B.M. and 28°K for CuMoO4, 1.71 B.M. and ? 12°K for Cu3Mo2O9, and 1.74 B.M. and ? 93°K for Cu4?xMo3O12. Below 200°K CuMoO4 becomes antiferromagnetic. Cu2Mo3O10 and Cu6Mo4O15 show weak temperature-independent paramagnetism. 相似文献
98.
Studies on 16-Membered Azothia- and Azoxythiacrown Ethers as Ion Carriers in Ion Selective Membranes
Jolanta Szczygelska-Tao Jan F. Biernat Łukasz Górski Elżbieta Malinowska 《Journal of inclusion phenomena and macrocyclic chemistry》2004,49(1-2):167-171
16-Membered azothia- and azoxythiacrown ethers have been studied as ion carriers in ion-selective membranes. Their selectivities towards alkali, alkaline earth, transition and heavy metal cations were evaluated. The complex formation constants for these compounds with chosen cations have been determined using segmented sandwich membranes method. 相似文献
99.
Colloidal noble metal-based nanoparticles are able to catalyze oxidation of chromogenic substrates by H2O2, similarly to peroxidases, even in basic media. However, lack of robust chromogens, which work in high pH impedes their real applications. Herein we demonstrate the applicability of selected catechol derivatives: bromopyrogallol red (BPR) and pyrogallol (PG) as chromogenic substrates for peroxidase-like activity assays, which are capable of working over wide range of pH, covering also basic values. Hyperbranched polyglycidol-stabilized gold nanoparticles (HBPG@AuNPs) were used as model enzyme mimetics. Efficiency of several methods of improving stability of substrates in alkaline media by means of selective suppression of their autoxidation by molecular oxygen was evaluated. In a framework of presented studies the impact of borate anion, applied as complexing agent for PG and BPR, on their stability and reactivity towards oxidation mediated by catalytic AuNPs was investigated. The key role of high concentration of hydrogen peroxide in elimination of non-catalytic oxidation of PG and improvement of optical properties of BPR in alkaline media containing borate was underlined. Described methods of peroxidase-like activity characterization with the use of BPR and PG can become universal tools for characterization of nanozymes, which gain various applications, among others, they are used as catalytic labels in bioassays and biosensors. 相似文献