Experimental densities,vapor pressures,and critical point,and a fundamental equation of state for dimethyl ether

Densities, vapor pressures, and the critical point were measured for dimethyl ether, thus, filling several gaps in the thermodynamic data for this compound. Densities were measured with a computer-controlled high temperature, high-pressure vibrating-tube densimeter system in the sub- and supercritical states. The densities were measured at temperatures from 273 to 523 K and pressures up to 40 MPa (417 data points), for which densities between 62 and 745 kg/m³ were covered. The uncertainty (where the uncertainties can be considered as estimates of a combined expanded uncertainty with a coverage factor of 2) in density measurement was estimated to be no greater than 0.1% in the liquid and compressed supercritical states. Near the critical temperature and pressure, the uncertainty increases to 1%. Using a variable volume apparatus with a sapphire tube, vapor pressures and critical data were determined. Vapor pressures were measured between 264 and 194 kPa up to near the critical point with an uncertainty of 0.1 kPa. The critical point was determined visually with an uncertainty of 1% for the critical volume, 0.1 K for the critical temperature, and 5 kPa for the critical pressure. The new vapor pressures and compressed liquid densities were correlated with the simple TRIDEN model. The new data along with the available literature data were used to develop a first fundamental Helmholtz energy equation of state for dimethyl ether, valid from 131.65 to 525 K and for pressures up to 40 MPa. The uncertainty in the equation of state for density ranges from 0.1% in the liquid to 1% near the critical point. The uncertainty in calculated heat capacities is 2%, and the uncertainty in vapor pressure is 0.25% at temperatures above 200 K. Although the equation presented here is an interim equation, it represents the best currently available.     

镉－硫氰酸根与铵－苯并15－冠－5配合物的合成与结构研究

用凝胶法生长了标题配合物［ＮＨ_４（Ｂ１５Ｃ５）_２］［Ｃｄ（ＳＣＮ）_３］的晶体，并对其进行了红外光谱，元素分析等各项物理性质的测试。经Ｘ射线单晶结构分析得到了配合物的全部晶体学数据：Ｍ_ｒ＝８４１．３１，正交晶系，空间群Ｐ２_１２_１２_１，晶胞常数ａ＝１０．９７０（３），ｂ＝２１．８３４（３），ｃ＝１５．５６３（４），Ｖ＝３７２７（３），Ｚ＝４，Ｄ_ｘ＝１．５０ｇ／ｃｍ￣３，Ｆ（０００）＝１７３６，μ＝７．０９ｃｍ￣（－１），Ｒ＝０．０７０，Ｒ_ｗ＝０．０６３。结构分析结果表明，配阳离子［ＮＨ_４（Ｂ１５Ｃ５）_２］￣＋和配阴离子［Ｃｄ（ＳＣＮ）_３］￣－间靠静电力结合成配合物。     

MELTING AND CRYSTALLIZATION BEHAVIOR OFAN AROMATIC POLY (AZOMETHINE ETHER) WITH NON-LINEARLY SHAPED MOLECULAR CONFORMATIONS

The melting and crystallization behavior have been investigated for an aromatic poly(azomethine ether) with non-linearly shaped molecular conformations. This polymer wasfound to undergo multiple melting processes and its phase transition behavior wasinfluenced sensitively by the thermal history of sample. A significant difference between thepolymer chain aggregation abilities of samples cooled from the different states wasobserved. The possible molecular morphology and aggregation models for describing thestructures of this polymer were proposed and discussed. The crystallization behavior of thesamples cooled from the partially isotropic state and the influence of cooling rate on it havealso been examined with DSC.     

Solvation of Calix[4]arene-bis-crown-6 Molecules

Single crystal X-ray diffraction analyses of calix[4]arene-bis-crown-6 (1) and calix[4]arene-bis-benzocrown-61,2-dichloroethane (2) are reported. Thesestructures offer an opportunity to study the conformation of calix[4]arene-bis-crown-6 molecules in the absence of solvent, and when very weakly solvated. These structures exhibit different conformations of the crown ring, and limited flexibility of the calix[4]arene,but do not show solvent or crown inclusion in the calix[4]arene cavity. Comparisons to similar structures are made, and the implications for cesium binding are discussed.     

Heterogeneous and homogeneous reduction of benzyl phenyl ether

By analyzing the kinetics of heterogeneous (electrode) and homogeneous reduction for benzyl phenyl ether it was found that toluene and phenol are formed via the transfer of two electrons and the breaking of the PhO-Bz bond. It was shown that electron transfer constitutes the slow stage in heterogeneous and homogeneous reduction. The homogeneous transfer coefficient was approximately 0.5, which represents a significant difference from the heterogeneous value.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan's Scientific Center, Russian Academy of Sciences, 420083 Kazan'. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1760–1765, August, 1992.     

Synthesis,characterization, and curing of well-defined allyl ether-maleate functional ester oligomers: Linear versus nonlinear structures

A series of allyl ether-maleate functional star-shaped esters with from one to four arms has been synthesized. The structures that have been made are an analogous series with increasing molecular weight and functionality where the increase in molecular weight has been made nonlinear, i.e., star-shaped. The resins are monodisperse in the sense that each arm has a well-defined structure and that, within a certain sample, only one type of molecule exists. The viscosity and rheological behavior of the resins have been studied. The curing kinetics of the star-shaped (branched) resins and the properties of the films formed have also been studied. These properties have been related to differences in functionality and to differences in the molecular architecture of the resins. © 1992 John Wiley & Sons, Inc.     

Method for determination of methyl tert-butyl ether in gasoline by gas chromatography

A simple method for the determination of methyl tert-butyl ether (MTBE) in gasoline has been developed. The separation of MTBE from other analytes was controlled by the use of gas chromatography–mass spectrometry in the full scan mode using the characteristic primary, secondary and tertiary ions m/z 73, 57 and 43. The sample mass spectrum did not show any superimposition of other analytes. The separation from the common gasoline component 2-methylpentane was sufficient for reliable quantitation. An application of the developed conditions using gas chromatography with flame ionization detection was performed by the analysis of regular, euro super, super premium unleaded and ‘Optimax’ gasoline from petrol stations in the area of Frankfurt/Main, Germany. Regular unleaded gasoline shows an average MTBE content of 0.4% (w/w), whereas the MTBE content in euro super gasoline varies between 0.4 and 4.2% (w/w). The blending of MTBE to super premium has increased from 8.2% (w/w) in 1998 to 9.8% (w/w) on average in 1999. The recently introduced gasoline ‘Optimax’ shows an average MTBE content of 11.9% (w/w). The presented method might also be used for the analysis of other ethers, such as ethyl tert-butyl ether, which requires the use of another internal standard.     

Solvent Modification in Ion-Pair Extraction: Effect on Sodium Nitrate Transport in Nitrobenzene Using a Crown Ether

A comparative quantitative analysis of the effect of solventmodifiers on the ion-pair extraction of an inorganic salt by a crown ether was conducted with the aim of advancing the understanding of transport of highly hydrophilic metal ions from aqueous salt solutions. Two classes of solvent modifiers that possess electron-pair donor (EPD) or hydrogen-bond donor (HBD) groups were investigated. The equilibrium constants corresponding to the extraction of sodium nitrate into nitrobenzene (NB) employing model neutral host cis-syn-cis-dicyclohexano-18-crown-6 (compound 1) with and without solvent modifier were determined using the SXLSQI computer model. For a series of EPD modifiers—including tri-n-butyl- and tri-phenylphosphate, tri-n-butyl- and tri-phenylphosphine oxide, N,N-di-n-butyl- and N,N-di-phenylacetamide—the enhancement of the NaNO₃ extraction by compound 1 was found to be dependent on the hydrogen-bond acceptance ability of the modifier as quantified by the β solvatochromic parameter. A HBD modifier 3,5-di-t-butylphenol (compound 8), which forms strong hydrogen bonds with nitrate anion in NB, exhibited even greater enhancement of the NaNO₃ extraction by compound 1. The determined extraction constants were correlated with the β- or α-solvatochromic parameters of the solvent modifiers and linear trends were observed. Hydrogen bond interaction between compound 8 and nitrate anion in the presence of the sodium-loaded crown ether in the extraction phaseswas studied by vibrational spectroscopy.     

N-取代氮杂冠醚的合成和络合萃取性能研究进展

综述了N-取代氮杂冠醚的合成和对金属离子的选择性络合和萃取研究的新进展.     

Lewis acid promoted aldol reaction of fluorinated silyl enol ethers from new fluoroacetylsilane derivatives

New fluorinated silyl enol ethers with various trialkylsilyl groups were synthesized. Various fluorinated β-hydroxy ketones were synthesized by Lewis acid promoted aldol reaction of silyl enol ethers with diverse aldehydes. Reactivity of various trialkylsilyloxy groups toward Lewis acid was also studied.