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: In this paper, a new reagent is proposed whose concentrations of peroxodisulphate and sodium hydroxide are founded on the stoichiometric relations at the autodecomposition of the peroxidisulate; the proper pH of 8.0 for the reduction is achieved by addition of the calculated amount of Tris(hydroximethyl)aminomethane hydrochloride.
124 citations
TL;DR: In this article, the rate constants for the reactions with ozone, UV radiation, and Fenton's reagent were determined by means of a competition kinetic model, and the results showed that reaction with OH radicals was the major pathway for the oxidative transformation of these compounds.
Abstract: Oxidation of three pharmaceuticals (primidone, ketoprofen, and diatrizoate sodium) by means of several advanced oxidation processes including such as ozonation, UV radiation, and Fenton’s reagent has been studied. The influence of operating variables was established, and first-order rate constants were determined in most of the oxidation systems. Specifically, for the reactions with ozone, the following rate constants were obtained by means of a competition kinetic model: 1.0 ± 0.1, 0.40 ± 0.07, and 0.05 ± 0.01 M−1·s−1, for primidone, ketoprofen, and diatrizoate, respectively. The results showed that reaction with OH radicals was the major pathway for the oxidative transformation of these compounds. In the photodegradation experiments by 254 nm radiation, the quantum yields were also determined for every compound at different pH and temperatures. Additionally, the competition kinetic model, which was also used in Fenton’s reagent experiments, allowed to evaluate the rate constants for the reaction with hy...
123 citations
TL;DR: In this article, the effects of the addition stage of the modifiers used in the synthesis of the resins and the type of modification reagent on the structures of the Resins and their molar masses and reactivities were investigated.
Abstract: Lignin-based chemicals, starch, and urea were used as modifiers for phenol–formaldehyde resol resins. The effects of the addition stage of the modifiers used in the synthesis of the resins and the type of modification reagent on the structures of the resins and their molar masses and reactivities were investigated. The modifications with corn starch and lignin promoted condensation; this was verified by increased molar masses and high ratios of methylene bridges to the sum of free ortho and para aromatic groups with respect to the corresponding reference resin without a modification reagent. The later the modifier was added to the resin condensation mixture, the more methylene bridges were formed with respect to the amounts of free ortho and para aromatic groups. In addition, when urea or wheat starch was added in the later condensation stage, the final condensation also reached high stages. The modifications with lignosulfonate and starch, as well as the early addition of urea, enhanced p–p′ bridge structures. The lowest condensation stage and, therefore, the highest reactivity were found when wheat starch was added with the starting reagents. The curing heat of the wheat-starch-modified resins decreased according to the deferred addition point of starch. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 582–588, 2003
123 citations
123 citations
TL;DR: The conversion of an alkenyl iodide bearing a keto group to the corresponding silylated cyanohydrin allows preparation of the corresponding Grignard reagent affording, after acylation and deprotection, unsaturated 1,4-diketones.
123 citations