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排序方式: 共有85条查询结果,搜索用时 93 毫秒
31.
Lynn M. Bradley Jeanne M. Lesica Kevin B. Albertson 《Reaction Kinetics and Catalysis Letters》1997,62(1):3-7
A series ofp-substituted benzyl alcohols have been oxidized to their corresponding aldehydes using aqueous hypochlorite and phase-transfer
catalyst (PTC) conditions. The reaction constant, p, has been determined to be +1.03. Possible mechanisms are suggested. 相似文献
32.
Polyethersulfone membranes are widely used for ultrafiltration and microfiltration especially in the dairy industry, but they are believed to degrade when exposed to the sodium hypochlorite solution that is used to sanitize the processing equipment. Such membranes were exposed to sodium hypochlorite for up to 25,000 ppm-day at 55 °C, and pH 9 and 12. Mechanical properties as measured by dynamic mechanical analysis and tensile strength did not change greatly, but surface properties measured by FTIR-ATR, field emission scanning electron microscopy and associated energy dispersive X-ray spectroscopy detected significant changes in the surface. Surface pitting was observed and was found to be most severe at pH 9. It was thought that pitting was the likely cause of degradation in performance of the membranes and that pits could act as stress raisers leading to cracking. 相似文献
33.
《Analytical letters》2012,45(17):3187-3197
Abstract A multicommutation flow system for the spectrophotometric determination of hypochlorite in bleaching products is proposed. In this system, N,N-diethyl-p-phenylenediamine (DPD) reacts with hypochlorite, and the product was monitored at 515 nm. The analytical curve for hypochlorite was linear in the concentration range from 2.68 × 10?5 to 1.88 × 10?4 mol L?1 (2–14 mg L?1) with a detection limit of 6.84 × 10?6 mol L?1 (0.51 mg L?1). The sampling rate was 45 h?1, and a relative standard deviation of 1.4% (n = 10) was obtained. The recovery of this analyte ranged from 97.2% to 102.5%, and the results found using the proposed spectrophotometric multicommutated flow system agreed with the data obtained using a reference method (iodometric titration) at the 95% confidence level. 相似文献
34.
35.
A rapid, efficient, economical, and easy-to-scale method for the effective conversion of carbamates to corresponding N,N-dichlorocarbamates by using sodium hypochlorite in acidic medium has been described. N,N-Dichlorocarbamates were obtained in quantitative yield through a simple workup in reduced reaction time.
36.
Te‐Haw Wu Dr. Ching‐Ping Liu Dr. Chih‐Te Chien Dr. Shu‐Yi Lin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(35):11672-11675
Herein, a promising sensing approach based on the structure fragmentation of poly(amidoamine) (PAMAM) dendrimers for the selective detection of intracellular hypochlorite (OCl?) is reported. PAMAM dendrimers were easily disrupted by a cascade of oxidations in the tertiary amines of the dendritic core to produce an unsaturated hydroxylamine with blue fluorescence. Specially, the novel fluorophore was only sensitive to OCl?, one of reactive oxygen species (ROS), resulting in an irreversible fluorescence turn‐off. The fluorescent hydroxylamine was selectively oxidised by OCl? to form a labile oxoammonium cation that underwent further degradation. Without using any troublesomely synthetic steps, the novel sensing platform based on the fragmentation of PAMAM dendrimers, can be applied to detect OCl? in macrophage cells. The results suggest that the sensing approach may be useful for the detection of intracellular OCl? with minimal interference from biological matrixes. 相似文献
37.
该文设计并合成了一种基于菲并咪唑的新型次氯酸荧光探针,该探针由商用试剂9,10-菲醌和4-(甲基巯基)苯甲醛通过一步反应生成,只需简单后处理(过滤和水洗)即可得到大量纯品(产率达85%)。由于硫的重原子效应,探针荧光较弱。但在次氯酸存在下,探针分子内的硫原子被氧化成亚砜,重原子效应减弱,同时分子内电荷转移效应(ICT)加强,导致荧光增强。借助高分辨质谱,证明了探针与次氯酸盐的反应机理。在PBS缓冲溶液中(DMF∶H_2O=2∶8,体积比,pH 7.4),探针MPI可定量检测0~100μmol/L范围内的HClO,检出限为0.26μmol/L。该探针对次氯酸具有较高的灵敏性和选择性。更重要的是,MPI具有良好生物相容性和细胞渗透性,可用于活细胞内次氯酸的可视化成像。探针MPI有望为机体内次氯酸的检测与追踪提供一种可靠、有效的方法。 相似文献
38.
Catechins, one of the class of flavonoids, are known as very efficient antioxidants. Here we investigated the kinetics of the reactions of three catechins, namely, catechin, epigallocatechin, and epigallocatechin gallate (EGCG) with some oxidants, which are formed in vivo under oxidative stress, hypochlorite, peroxynitrite, and amino acid peroxyl radicals. Stopped-flow spectrophotometry and pulse radiolysis technique with absorption detection were used to observe the formation of intermediate products of oxidized catechins. We found that catechins react with hypochlorite with the rate constant of the order of 105–106 M−1 s−1 at pH 7.4. Experimental kinetic traces of the reaction of EGCG with valine peroxyl radicals were fitted using chemical simulation, and the rate constant of this reaction was found to be 5 × 105 M−1 s−1. The rate constants of the formation of unstable catechin quinones in the reaction with peroxynitrite were comparable to that of spontaneous peroxynitrite isomerization, which indicates that catechins are oxidized indirectly by peroxynitrite. Biological consequences of these reactions are discussed. 相似文献
39.
Identification and Spectroscopic Characterization of Nonheme Iron(III) Hypochlorite Intermediates
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Dr. Apparao Draksharapu Davide Angelone Dr. Matthew G. Quesne Sandeep K. Padamati Dr. Laura Gómez Dr. Ronald Hage Prof. Dr. Miquel Costas Prof. Dr. Wesley R. Browne Dr. Sam P. de Visser 《Angewandte Chemie (International ed. in English)》2015,54(14):4357-4361
FeIII–hypohalite complexes have been implicated in a wide range of important enzyme‐catalyzed halogenation reactions including the biosynthesis of natural products and antibiotics and post‐translational modification of proteins. The absence of spectroscopic data on such species precludes their identification. Herein, we report the generation and spectroscopic characterization of nonheme FeIII–hypohalite intermediates of possible relevance to iron halogenases. We show that FeIII‐OCl polypyridylamine complexes can be sufficiently stable at room temperature to be characterized by UV/Vis absorption, resonance Raman and EPR spectroscopies, and cryo‐ESIMS. DFT methods rationalize the pathways to the formation of the FeIII‐OCl, and ultimately FeIV?O, species and provide indirect evidence for a short‐lived FeII‐OCl intermediate. The species observed and the pathways involved offer insight into and, importantly, a spectroscopic database for the investigation of iron halogenases. 相似文献
40.