Selectivity optimization for the capillary gas chromatographic analysis of bacterial cellular fatty acids

Summary The importance of selectivity in the capillary gas chromatographic analysis of the cellular fatty acids of micro-organisms is underestimated. The analysis on apolar silicone phases can lead to erratic elucidation of the fatty acid structure. Qualitative errors have been detected in commercially available standards on which computer matching identification techniques are based. Using highly polar capillary columns of the cyanopropyl silicone type, the errors could be elucidated. The exact identification of the hydrolysis products of bacteria is a must for chemotaxonomic studies applying chromatographic techniques. The fatty acid methyl ester profiles can also contain other chemical components which are very important taxonomic markers. Fatty aldehydes, for example, are main components in someClostridium species. Fractionation techniques are described for selective enrichment of fatty aldehydes and hydroxy fatty acids.Dedicated to Prof. Dr. A Liberti on the occasion of his 70th birthday     

Bis-substituted benzo-15-crown-5 ethers as ion carriers in potassium ion-selective electrodes

Lipophilic bis-substituted ester and ether derivatives of benzo-15-crown-5 have been synthesised. The correlation between the structure and potentiometric ion-selectivity has been studied in PVC membrane ion-selective electrodes. An ion-selective potassium sensitive electrode based on 4,5-bis (biphenyloxymethyl)benzo-15-crown-5 exhibited the best electrode properties. The detection limit was loga _K = -5.4; logK _K,Na ^ppot = -3.5. The effect of the lipophilicity of neutral carriers upon electrode performance has been also discussed.     

Supramolecular approaches to generate libraries of chelating bidentate ligands for homogeneous catalysis

The process of catalyst discovery and development relying on combinatorial methods has suffered so far from the difficult access to structurally diverse and large libraries of ligands, in particular the structurally more complex class of bidentate ligands. A completely new approach to streamline the difficult ligand synthesis process is to use structurally less complex monodentate ligands that self-assemble in the coordination sphere of a metal center through noncovalent attractive ligand-ligand interactions to generate bidentate, chelating ligands. When complementary attractive ligand-ligand interactions are employed, it is even possible to generate libraries of defined chelate-ligand catalysts by simply mixing two different monomeric ligands. This Minireview summarizes the first approaches and results in this new field of combinatorial homogeneous catalysis.     

Polymer-protected palladium nanoparticles. Morphologies and catalytic selectivities

Colloidal palladium nanocatalysts prepared by in situ reductions of palladium chloride were immobilized and protected by either of two water-soluble polymers. The particle sizes and size distributions of the palladium colloids were determined by transmission electron microscopy. Their selectivities as catalysts were determined by comparing the extents of hydrogenation of carefully chosen pairs of small-molecule olefins. There was found to be high hydrogenation selectivity with regard to cyclic vs. noncyclic olefins. Selectivity was relatively low, however, among olefins that differed only in size (such as hexene vs. octene), or olefins differing only with regard to the positions of the double bonds (such as 1-octene vs. 3-octene). Selectivity could be improved by careful choice of the immobilizing polymer, and by its use at relatively high concentrations.     

铁-钼/活性炭催化剂的费-托合成反应性能

用微型固定床反应器和原位穆斯堡尔谱考察了在活性炭担载的铁-钼双金属催化剂上的费-托合成反应和在反应条件下的物相。已知在费-托合成中铁有利于生成长链烃,钼有利于生成低碳烃。铁-钼/活性炭催化剂则综合了铁和钼的性质,其中铁-钼/油棕炭催化剂具有很好的活性和液化石油气选择性。在反应中,富钼催化剂的主要物相为铁-钼碳化物,而富铁催化剂的物相则为铁-钼碳化物和e’-Fe_2·2C碳化铁。     

Selectivity of long chain stationary phases in reversed phase liquid chromatography

A series of commercial monomeric and polymeric C(18), C(27), and C(30) stationary phases were compared with immobilized poly(ethylene-co-acrylic acid) stationary phases synthesized in-house. The columns were characterized on the basis of methylene selectivity, silanol activity, metal activity, pore size, shape selectivity, and the ability to separate tocopherol isomers and carotenoid isomers. Monomeric and polymeric C(30) phases were shown to yield excellent separations of the tocopherol isomers while the polymeric C(30) and polyethylene phases were more appropriate to the separation of carotenoids.     

对钠离子有选择性的中性载体

合成了十一种中性离子载体,用它们制成钠离子选择性电极,测定了电极的选择性系数并与文献报道的类似电极进行了比较。     

高分子气体分离膜材料的化学结构与气体透过性能之间的关系

本文以硅橡胶和聚酰亚胺为基础,从高分子的化学组成、分子链段的运动能力、侧基的大小及其作用等几个方面,讨论了聚合物的化学结构对其均质膜的气体选择透过性能的影响,以溶解扩散过程对气体分离膜材料的透气行为进行了剖析,井简述高分子化学结构对其成膜时结晶情况的影响及对气体透过的作用;还概述了气体分离膜科学发展的历史以及基本原理.     

Inclusion by a fluorenyl diol host with substituted pyridines

The structures of the inclusion compounds formed by the host 9,9’-(ethyne-1,2-diyl)bis(fluoren-9-01) with pyridine and picolines are similar and display tubular topology. The host discriminates poorly between these guests. The kinetics of desorption of the pyridine compound is governed by the Avrami-Erofe’ev equation A2, with an activation energy of 111(7) kJ mol⁻¹.     

Selective synthesis of di(propen-1-yl)sulfone and di(propen-1-yl)sulfoxide

Convenient selective methods of synthesis of the title compounds, based on oxidation of di(propen-1-yl)sulfide with 30% H₂O₂, have been developed.Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, 664033 Irkutsk. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 675–679, March, 1992.