The effect of olefinic terminal chains on the mesomorphic properties of 4,4′-disubstituted diphenyldiacetylenes

New diphenyldiacetylenes of the type with A, B = H and/or F; m = 0, 1; n = 1–4; and X = C _n H_2n+1, F, CF₃ or CN were synthesized and their mesomorphic properties determined by hot stage polarizing microscopy and DSC. When m = 0, all of these compounds showed only a nematic phase except when X = CF₃ when both nematic and smectic A phases were seen. Both clearing and melting temperatures were higher than those reported for substitution with the corresponding alkyl chains but the much larger increase in clearing temperatures produced considerably wider nematic phases. Eutectic mixtures of a few of these olefins yielded nematic materials also having much wider temperature ranges and higher clearing temperatures than the eutectic mixtures of the alkyl compounds, while retaining their high birefringence and low viscosities. Such materials are of interest for beam-steering devices. Four of the diacetylenes with m = 1 (A, B = H) were also prepared (X = C₆H₁₃, F, n= 2, 3). When X was C₆H₁₃ (n=2), the nematic range was smaller in the 2- than in the 1-olefin but wider than in the alkyl series. When X=F, either no nematic phase or a monotropic one was observed, whereas the 1-olefins gave a much wider nematic phase. Both transition temperatures were lower than those for the corresponding 1-olefin and alkyl analogues. The compound with X=C₆H₁₃ and n=2 had a melting temperature below room temperature.     

ON INVERSES AND ALGEBRAIC LOOPS OF CO-H-SPACES

In this paper we study the properties of homotopy inverses of comultiplications and Mgebraic loops of co-H-spaces based on a wedge of spheres. We also investigate a method to construct new comultiplications out of old ones by using a group action. We are primarily interested in the algebraic loops which have inversive, power-associative and Moufang properties for some comultiplications.     

采用柠檬酸合成高分散铜催化剂用于选择氢解反应

A highly dispersed Cu catalyst supported on silica was prepared by an incipient wetness impregnation method with citric acid.The synthesis was studied by nitrogen physisorption,X-ray diffraction,and temperature-programmed reduction by comparing with a reference prepared without citric acid.The catalyst precursor obtained after impregnation was X-ray amorphous.The precursor was readily transformed to crystalline CuO upon calcination.The CuO particles were of uniform size in a highly dispersed state and can be reduced to Cu at a lower temperature.The activity of the Cu catalyst obtained was an order of magnitude higher than that of the reference for the hydrogenolysis of methyl laurate to dodecanol.     

苯甲酸分子印迹聚合物的制备及其吸附性能

以苯甲酸为模板分子,4-乙烯基吡啶为功能单体,乙二醇二甲基丙烯酸酯为交联剂,采用本体聚合法制备了高选择性识别的分子印迹聚合物。利用合成的聚合物作为吸附剂填充制备气体浓缩针装置,并用于挥发性有机化合物(VOCs)的气相色谱分析。实验结果表明:60℃下恒温聚合反应6h,模板分子、功能单体、交联剂的物质量比为1∶4∶20,预聚合时间为3h,溶剂为乙腈,模板分子为苯甲酸时,合成的分子印迹聚合物对苯系物的吸附量最大。     

THE δ^－－PROBLEM FOR HOLOMORPHIC （0,2）－FORMS ON PSEUDOCONVEX DOMAINS IN SEPARABLE HILBERT SPACES AND D.F.N. SPACES

This paper shows that the δ^--problem for holomorphic (0, 2)-forms on Hilbert spaces is solv-able on pseudoconvex open subsets. By using this result, the authors investigate the existence ofthe solution of the δ^--equation for holomorphic(0, 2)-forms on pseudoconvex domains in D.F.N.spaces.     

ChemInform Abstract: C61 Clusters: AM1 Computations.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

ChemInform Abstract: Si60 Clusters: AM1 Computed Ih/C2v Relative Populations

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

ChemInform Abstract: Quantitative Photoabsorption and Fluorescence Study of HCl in Vacuum Ultraviolet.

The oscillator strengths for the discrete structures are determined from the measured absorption cross sections; the values are comparable to theoretical results.     

ChemInform Abstract: Vibrational Spectroscopy of the Hydrated Hydronium Cluster Ions H3O+·(H2O)n (n = 1, 2, 3).

Using a new spectroscopic method, the gas phase IR spectra of the title cluster ions, produced in a high pressure corona discharge source, are observed between 3550 and 3800 cm^-1.     

ChemInform Abstract: Vibrational Spectroscopy of the Ammoniated Ammonium Ions NH+ 4(NH3)n ( n = 1-10)

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.