An effective force field for molecular dynamics simulations of dimethyl sulfone

A rigid five-site united atom model for dimethyl sulfone (DMSO₂) compatible with the GROMOS force field is parametrized and tested. The parameters were optimized with respect to experimental quantities such as liquid density, heat of vaporization, shear viscosity and excess free energy. Good agreement with pure component properties is achieved except for the static dielectric permittivity which is calculated too low. Together with the SPC model for water the new DMSO₂ model was used to study aqueous mixtures at low concentrations and compared to aqueous mixtures of DMSO. It is concluded that interaction parameters for sulfoxide oxygen are not directly transferable to sulfonyl oxygen.     

Catalytic activity of CeO2 and Pr2O3 for the liquid-phase benzylation of o-xylene to 3,4 – dimethyldiphenylmethane

The liquid phase benzylation of o-xylene with benzyl chloride over rare earth oxide catalysts like CeO₂ and Pr₂O₃ was studied in a batch reactor at atmospheric pressure and 363 K. Surface area, pore volume, DTA, acid strength distribution on the catalyst surface and optimum temperature of the catalyst are reported.     

Photoinduced and thermally induced cationic polymerizations using S,S‐dialkyl‐S‐(3,5‐dimethylhydroxyphenyl)sulfonium salts

A study of the photoinitiated and thermally initiated cationic polymerizations of several monomer systems with S,S‐dialkyl‐S‐(3,5‐dimethylhydroxyphenyl)sulfonium salt (HPS) photoinitiators bearing different lengths of alkyl chains on the positively charged sulfur atom has been conducted. HPS photoinitiators are capable of photoinitiating the cationic polymerization of a wide variety of epoxy and vinyl ether monomers directly on irradiation with short‐wavelength UV light. Aryl ketone photosensitizers are effective in extending the spectral response of these photoinitiators into the long‐wavelength UV region. Kinetic studies with real‐time infrared spectroscopy show that HPS photoinitiators exhibit good efficiency in the polymerization of epoxide and vinyl ether monomers. Comparative studies also demonstrate that S,S‐dimethyl‐S‐(3,5‐dimethyl‐2‐hydroxyphenyl)sulfonium salts are more active photoinitiators than their isomeric S,S‐dimethyl‐S‐(3,5‐dimethyl‐4‐hydroxyphenyl)sulfonium salt counterparts. Both types of HPS photoinitiators display reversible photolysis as a result of facile termination reactions that take place between the growing chains ends with the photogenerated sulfur ylides. Preliminary studies have shown that HPS photoinitiators can also be employed as thermal initiators for the cationic ring‐opening polymerization of epoxides at moderate temperatures. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2570–2587, 2003     

Millimeter and submillimeter wave measurements of complex optical and dielectric parameters of materials

These coolant materials were chosen for the first in this series of measrements of the complex parameters of liquids over the entire millimeter and submillimeter wavelength range of the spectrum. The fluorocarbon coolants not reported here exhibit an order of magnitude lower loss. It is the characteristic of these liquids that the absorption coefficient increases monotonically with frequency.Partially supported by the Office of Fusion Energy, U.S. Department of Energy, under Contract W-7405-eng-26 with Union Carbide Corporation.Supported by the National Science Foundation.     

O,N-Dimethylation of 5,6-dihydroxynicotinic acid

AnO,N-dialkylation product, 1-methyl-5-metlioxy-6-oxo-1,6-diliydropyridine-3 carboxylic acid, is formed in the reaction of 5,6-dihydroxynicotinic acid with dimethylsulfate.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1554–1555, June, 1996.     

21世纪的绿色燃料--二甲醚

介绍了二甲醚作为一种新型清洁燃料的开发利用状况，探讨了山西省发展煤基合成二甲醚进行煤炭深加工的必要性和现实性。     

Confusion between dimethyl selenenyl sulfide and dimethyl selenone released by bacteria

Dimethyl selenone [(CH₃)₂SeO₂] has been reported in the literature as a metabolite released by bacteria in contact with selenium metal or selenium salts. In this study, mass spectral, chromatographic, and boiling-point data are presented that show that dimethyl selenone has been confused with dimethyl selenenyl sulfide (CH₃SeSCH₃). In addition, the headspaces above monocultures of selenium-resistant bacteria were examined using gas chromatography followed by fluorine-induced chemiluminescence detection. A number of alkyl sulfur and selenium species were detected, along with dimethyl selenenyl sulfide. A pathway from oxidized selenium salts to reduced methylated selenides and dimethyl selenenyl sulfide is also presented.     

二甲醚发动机燃料喷射过程及其影响因素研究

在一台2102QB二甲醚发动机上测量了高压油管两端的压力,在不同的发动机转速、负荷和不同的二甲醚燃料温度条件下比较了泵端、嘴端高压油管的压力,结合喷油器针阀升程信号计算了二甲醚燃料的喷射延迟期和持续期,以及不同二甲醚温度条件下的声速.试验结果表明:二甲醚的弹性模量小,压缩性大,喷射延迟期较柴油的长;二甲醚的温度对喷射的最高压力、持续期和压力波传播速度均有较大影响,二甲醚发动机的供油提前角需要根据发动机的转速和燃料温度重新匹配.