持久性二烷基硝基氧化物(例如,2,2,6,6-四甲基哌啶-1-氧基,TEMPO)在受阻胺光稳定剂 (HALS) 添加剂的活性中起核心作用,该添加剂可抑制消费品和工业品的(光)氧化降解产品。HALS 的公认机制包括一个催化循环,该循环涉及硝基氧化物与烷基自由基的快速结合以产生烷氧基胺,该烷氧基胺随后与过氧基自由基反应以最终重新形成硝基氧化物。在此,我们提供了支持替代反应机制的证据,该机制涉及硝基氧与过氧自由基的酸催化反应以产生氧代铵离子,然后电子从烷基自由基转移到氧代铵离子以重新形成氮氧化合物。在前期工作中,我们表明 TEMPO 在酸存在下以扩散控制的速率与过氧自由基反应。现在,我们表明 TEMPO 可以通过与烷基反应从其氧铵离子再生。我们已经确定,该反应被认为是 TEMPO 催化合成转化中的关键步骤,发生在 k ∼ 1-3 × 10(10) M(-1) s(-1) 中,从而使其能够与 O2
ESR Studies on Chain Transfer Reactions: Rate Constants for the Reactions of Model Radicals of Polystyrene Growing Chain Ends with Tetrahalomethanes and Thiophenols
作者:Yoko Kuwae、Mikiharu Kamachi
DOI:10.1246/bcsj.62.2474
日期:1989.8
absolute rate constants for reactions of the model radicals of the growing chain ends of styrene and methacrylonitrile with tetrahalomethanes and thiophenols were determined by spin-trapping methods using ESR spectroscopy. The model radicals were produced by the photodecomposition of 1,1′-diphenylazoethane and 2,2′-azobisisobutyronitrile. In the case of the styrene model radical, the rate constants
New Ru(II) pyrazolone complex catalyzed direct amination of alcohols: A preliminary mechanistic investigation
作者:Sivadasan Dharani、Giriraj Kalaiarasi、Vincent M. Lynch、Rathinasabapathi Prabhakaran
DOI:10.1002/aoc.7076
日期:——
A novel Ru(II) complex containing 4-(2-hydroxybenzyl)-3-methyl-5-oxo-2,5-dihydropyrazole-1-carbothioic acid methylamide has been applied as a catalyst for directly aminating alcohols. Preliminary investigation on the reaction mechanism has been done with the help of NMR spectroscopy recorded for regenerated catalysts and an NMR reaction. In addition, a plausible mechanism for the formation of the coupled