聚酰亚胺中空纤维膜用于甲醇/甲基叔丁基醚的分离

甲醇／甲基叔丁基醚混合物的膜法分离，大多采用渗透汽化方法，少有采用蒸汽渗透法。用聚酰亚胺中空纤维膜，对以蒸汽渗透和渗透汽化两种方式分离甲醇／甲基叔丁基醚混合物（甲醇质量分数为0．01－0．30）的效果进行了对比。结果显示，在甲醇质量分数低于0．05时，蒸汽渗透较渗透汽化法的分离性能优越。     

Analysis with the electronic polaroscope

Analysis by means of oscillographic polarography with alternating current is discussed and illustrated by luminous diagrams showing tlie dependence $\text{dV}\text{dt}$—V. The quantity of the depolarizer can be determined either by the area of the cut-in on the diagram or by a comparative titration method.Practical examples are given in oscillographic analysis of various sulphonamides, local anaesthetics, purine derivatives, alkaloids, pyridin carboxylic acids, vitamins, antibiotics, hormones, etc.     

Replacing the carbonyl's oxygen with the difluoromethyl group

Aldehydes or ketones were reacted with 2-(trimethylsilyl)-1,3-dithiane (1) and the products reduced to the corresponding dithianes using tetrafluoroboric acid and sodium borohydride. These sulfur containing compounds were reacted with bromine trifluoride under mild conditions (1-2 min, 0 °C) with a net result of replacing the carbonyls' oxygen with the desired difluoromethyl moiety.     

Modifying Cellulose with the Emulsion of the Triazine Derivative Containing the Tertiary Amino Group to Improve the Reactivity with Reactive Dyes

Chemical modification of cellulose fabric with the emulsion of the triazine derivative containing the tertiary and quaternary amino groups was investigated. Chemical modified cellulose fabric could catalyze itself with reactive dyes containing chorotriazine group. Compared with unmodified cellulose, the modified cellulose could be dyed with reactive dyes under neutral or weakly acidic condition without the addition of salt. The color yield was higher than that of the unmodified cellulose, despite of the addition of large amounts of salt and alkali in the latter case and the modified cellulose got better wash fastness.     

15-Hydroxybenzomonothia-15-crown-5 with the sulfur atom linked with the benzene ring and the derived sulfoxide: synthesis,structure, and complexation with the metal cations

Novel 15-hydroxybenzomonothia-15-crown-5 containing the sulfur atom linked with the benzene ring and its S-oxide were synthesized. The stability constants for the complexes of the obtained benzocrown ethers and a reference 15-hydroxybenzo-15-crown-5 with Na, Ca, Ag^I, Cd, Hg^II, and Pb^II perchlorates were determined by ¹H NMR titration. In MeCN-d₃, the benzothiacrown ether demonstrates a high selectivity towards the thio- and oxothiophilic Hg²⁺ (logK ₁ = 7.1) and Pb²⁺ ions (logK ₁ = 7.4). In MeCN-d₃-D₂O mixtures, the stabilities of the most of complexes decrease sharply due to competitive hydration of the metal cations except for the “soft” Ag⁺ and Hg²⁺ ions having low affinity for the “hard” oxygen atoms and, on the contrary, very high affinity for the “soft” S^II atoms. This results in the change in selectivity of complexation: at the water content in solution of 20%, the benzothiacrown ether binds preferably the Hg²⁺ (logK ₁ = 5.0) and Ag⁺ ions (logK ₁ = 2.7). In MeCN-d₃, the benzothiacrown-derived sulfoxide is a weak and non-selective complexing agent towards all the metal cations under study; the reference 15-hydroxybenzo-15-crown-5 forms more stable complexes with the oxophilic sodium, calcium, and lead(ii) cations. The conformational features of the benzocrown ethers and their metal complexes established by NMR spectroscopy and X-ray diffraction are discussed. The found characteristics of the complexing ability of benzomonothia-15-crown-5 where the sulfur atom is in conjugation with the benzene ring reveal that the macrocyclic ligands with such a structure are promising as high-selective and efficient complexing agents for the “soft” mercury(ii) and silver(i) cations in acetonitrile-water mixtures.     

Solvent interactions with the indole chromophore

Comparison of solvent behaviour upon indole, N-methylindole, 5-methoxyindole and benzimidazole, both at the first S₁(¹L_a, ¹L_b) and second S₂(¹B_b) excited states, provides new information upon solvent interactions for the biologically important indole chromophore.     

Interrupting the Nazarov cyclization with indoles

A carbon-terminated interrupted Nazarov reaction is described. The trimethylsilyl enol ethers derived from propargyl vinyl ketones undergo selective proton transfer at the distal acetylenic carbon atom to provide allenyl vinyl ketones as transient intermediates. In the presence of indoles, a cascade of reactions is initiated that converts the initially formed pentadienyl cations to cyclopentenones bearing a quaternary alpha carbon atom.     

Investigation on the Se-Acylation with N-Acylbenzotriazoles

Abstract

The acylation of Se-nucleophiles with N-acylbenzotriazoles was investigated. Samarium phenylselenolate and benzylselenolate (RSeSmI₂) reacted with N-aroyl and N-alkanoylbenzotriazoles smoothly and afforded the corresponding selenol esters in good yields. Treatment of the RSeSmI₂ with α,β-unsaturated N-acylbenzotriazoles afforded the anticipated α,β-unsaturated selenol esters in moderate yields, due mainly to the side reaction of conjugate addition.

GRAPHICAL ABSTRACT      

Macromolecular systems with the p-type conductivity

General concepts of organic (polymeric) electronics are given, a relationship between chemical structure of semiconducting macromolecular systems and their electronic properties is considered, main approaches to the control of these properties are listed. A relationship between dimensionality of the systems considered (one-, two-, and three-dimensional) and a possibility to control their molecular organization, as well as their practical use are illustrated. Typical representatives of both the linear and branched (two- and three-dimensional) macromolecules, approaches to the synthesis of such macromolecules, their optical and electrical properties, as well as prospective fields of application, are considered.     

Hitting the target with bifunctional phage

Peptide libraries are rich sources of cell-targeting peptides. In this issue of Chemistry & Biology, Pasqualini and coworkers have developed a chimeric cell-targeting phage system that can easily be modified to delivery of a variety of reagents without need for chemical conjugation.     

Surface studies with the vacuum microbalance

This paper is generally concerned with presenting a broad overview of the capabilities, limitations, and potential uses of the vacuum ultramicrobalance for Surface studies. Determination of micromass changes of samples in vacuum and controlled gaseous environments at various temperatures is one of the powerful methods for studying surfaces. The traditional application of the vacuum microbalance and accompanying theoretical foundation for obtaining surface areas, activation energies of adsorption and desorption, the heat of adsorption, and the initial stages of oxidation are reviewed. As with most physical measurements, the simultaneous measurement of mass change and other parameters greatly increases the ability to understand physical and chemical processes. Examples of the combined measurement of residual gases, infrared spectroscopy, and electrical properties as well as the mass change are presented. Recent progress in developing an automated ultramicrobalance for operation in a UHV system combined with RGA and AES is discussed. Information about specific gas-solid systems is presented to illustrate the utility of the microbalance.     

Mending the bones with natural products

In this issue, Qiu and colleagues [1] demonstrate in vitro and in vivo activity of a triterpene glycoside from black cohosh. The isolated compound acts as a suppressor of osteoclastogenesis, targeting specifically RANKL, a member of the TNF superfamily.     

Nuclear shieldings with the SSB-D functional

The recently reported SSB-D functional [J. Chem. Phys. 2009, 131, 094103] is used to check the performance for obtaining nuclear magnetic resonance (NMR) shielding constants. Four different databases were studied, which contain a diversity of molecules and nuclear shielding constants. The SSB-D functional is compared with its "parent" functionals (PBE, OPBE), the KT2 functional that was designed specially for NMR applications and the coupled cluster CCSD(T) method. The best performance for the experimentally most-used elements ((1)H, (13)C) is obtained for the SSB-D and KT2 functionals.     

Electrometric titrations with the gold electrode

Summary Massive gold because of the passivity of the oxide formed on its surface can be used as a substitute for platinum in electrometric titrations including acid-base and oxidation-reduction systems. The end points are attended with large jumps on the curves and coincide satisfactorily with those obtained using the hydrogen or platinum electrode or by other method.     

Heterocycles with the bridgehead N atom

2,3,5,7-Tetramethyloxazolo[3,2-a]pyrimidinium perchlorate in reactions with sodium hydroxide, sodium ethoxide, and pyrrolidine undergoes earlier unknown recyclization into 1-substituted pyrrolo[1,2-c]pyrimidines. Recyclization of the same salt under the action of ammonia gives 2,3,5,7-tetramethylimidazo[1,2-a]pyrimidine. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1611–1614, August, 2007.