Zeolite HY and Silica Gel as New and Efficient Heterogenous Catalysts for the Synthesis of Triarylimidazoles under Microwave Irradiation

 Zeolite HY and silica gel efficiently catalyzed the three component condensation of benzil, benzaldehyde derivatives, and ammonium acetate under solvent-free conditions and microwave irradiation.     

Production of Siderophores by an Apple Root-Associated Streptomyces ciscaucasicus Strain GS2 Using Chemical and Biological OSMAC Approaches

Apple Replant Disease (ARD) is a significant problem in apple orchards that causes root tissue damage, stunted plant growth, and decline in fruit quality, size, and overall yield. Dysbiosis of apple root-associated microbiome and selective richness of Streptomyces species in the rhizosphere typically concurs root impairment associated with ARD. However, possible roles of Streptomyces secondary metabolites within these observations remain unstudied. Therefore, we employed the One Strain Many Compounds (OSMAC) approach coupled to high-performance liquid chromatography-high-resolution tandem mass spectrometry (HPLC-HRMSⁿ) to evaluate the chemical ecology of an apple root-associated Streptomyces ciscaucasicus strain GS2, temporally over 14 days. The chemical OSMAC approach comprised cultivation media alterations using six different media compositions, which led to the biosynthesis of the iron-chelated siderophores, ferrioxamines. The biological OSMAC approach was concomitantly applied by dual-culture cultivation for microorganismal interactions with an endophytic Streptomyces pulveraceus strain ES16 and the pathogen Cylindrocarpon olidum. This led to the modulation of ferrioxamines produced and further triggered biosynthesis of the unchelated siderophores, desferrioxamines. The structures of the compounds were elucidated using HRMSⁿ and by comparison with the literature. We evaluated the dynamics of siderophore production under the combined influence of chemical and biological OSMAC triggers, temporally over 3, 7, and 14 days, to discern the strain’s siderophore-mediated chemical ecology. We discuss our results based on the plausible chemical implications of S. ciscaucasicus strain GS2 in the rhizosphere.     

Über die Einwirkung von Wasser auf das Pentamethylenbromid

Ohne Zusammenfassung     

Zur Problematik individueller thermodynamischer Aktivitätskoeffizienten einzelner Ionensorten in Elektrolytlösungen hoher Konzentration

On the Individual Thermodynamic Activity Coefficients of Single Ion Species in Electrolyte Solutions at High Concentrations The individual activity coefficients of the single ion species, which are produced by dissociation of aqueous electrolytes, are necessary for the thermodynamic treatment of equilibrations and processes involving electrolytes. The determination of these values is one of the basic quests of electrochemistry and a controversial topic. This problem is unsolvable using classical thermodynamics. In this paper a mathematical method is shown, which can be used to split the mean activity coefficients into the values for the individual ion species of an electrolyte. For this determination the mean activity coefficients have to be expressed in the power form of equation. The concept based on the adaptation of a product function for the concentration development of the mean activity coefficients to the experimental data and their separation into factor functions of a predefined structure, which represent the concentration development of the individual activity coefficients of the single ion species of the electrolyte. This mathematical method was used to calculate the individual activity coefficients of the single ion species of alkali chlorides, alkaline earth chlorides, alkaline earth perchlorates, hydrohalic acids and alkali hydroxides. In summary, all the calculated single ion activity coefficients are in good agreement with the expected theoretical considerations. A proportionality to the reciprocal diameter of the unhydrated cation is clearly recognizable. The calculated individual activity coefficients correspond in every case with the assumption about their size, which can be reproduced using a variety of electrochemical investigations and experiments.