Topic
Reagent
About: Reagent is a research topic. Over the lifetime, 60091 publications have been published within this topic receiving 1234928 citations. The topic is also known as: reagens.
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TL;DR: A new approach to preparative organic synthesis in aqueous–organic systems is suggested, based on the idea that the enzymatic process is carried out in a biphasic system “water–water‐immiscible organic solvent,” which eliminates the traditional problem of stabilizing the enzyme against inactivation by a nonaqueous solvent.
Abstract: A new approach to preparative organic synthesis in aqueous–organic systems is suggested. It is based on the idea that the enzymatic process is carried out in a biphasic system “water–water-immiscible organic solvent.” Thereby the enzyme is localized in the aqueous phase—this eliminates the traditional problem of stabilizing the enzymes against inactivation by a nonaqueous solvent. Hence, in contrast to the commonly used combinations “water–water-miscible organic solvent,” in the suggested system the content of water may be infinitely low. This allows one to dramatically shift the equilibrium of the reactions forming water as a reaction product (synthesis of esters and amides, polymerization of amino acids, sugars and nucleotides, dehydration reactions, etc.) toward the products. The fact that the system consists of two phases provides another very important sources for an equilibrium shift, i.e., free energies of the transfer of a reagent from one phase to the other. Equations are derived describing the dependence of the equilibrium constant in a biphasic system on the ratio of the volumes of the aqueous and nonaqueous phases and the partition coefficients of the reagents between the phases. The approach has been experimentally verified with the systhesis of N-acetyl-L-tryptophan ethyl ester from the respective alcohol and acid. Porous glass was impregnated with aqueous buffer solution of chymotrypsin and suspended in chloroform containing N-acetyl-L-tryptophan and ethanol. In water (no organic phase) the yield of the ester is about 0.01%, whereas in this biphasic system it is practically 100%. The idea is applicable to a great number of preparative enzymatic reactions.
197 citations
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TL;DR: In this paper, the degradation of Rhodamine B, a waste dye effluent, has been studied using a hydrodynamic cavitational reactor with intensification studies in the presence of hydrogen peroxide, carbon tetrachloride and Fenton's reagent as possibly intensifying additives.
197 citations
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TL;DR: Evidence of the presence of reactions different from the hydroxyl radical oxidation was observed from comparison of the simultaneous Fenton's or UV/H2O2 oxidations of p-hydroxybenzoic acid, tyrosol and p-coumaric acid.
197 citations
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TL;DR: The quantitative description of these complexes in solution and the solid state provides the basis for predictions of interference from DTT in studies of metal ion binding of thiol-containing biomolecules.
196 citations
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TL;DR: In this article, the authors investigated the catalytic etherification of glycerol with tert-butyl alcohol in the presence of lab-made silica supported acid catalysts.
Abstract: The heterogeneous catalytic etherification of glycerol with tert- butyl alcohol was investigated in presence of lab-made silica supported acid catalysts. As reference, two commercial acid ion-exchange resins were also used. Experiments were carried out in batch mode at T R ranging from 303 to 363 K. An increase in reaction temperature favors the formation of di -substituted ethers. The etherification reaction proceeds according to a consecutive path and the surface reaction between adsorbed glycerol and protonated tert -butanol (tertiary carbocation) can be considered as the rate determining step. Steric hindrance phenomena and water hinder the formation of tri -substituted ether (TBGE). As expected, water removal was necessary to allow the higher ethers formation. The specific activity (turnover frequency, TOF ) of A-15 catalyst is significantly higher than that of the other studied acid systems, due to the wide pore diameter that allows an easier accessibility of the reagent molecules.
195 citations