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This article analyzes the kinetics of the decomposition of N-Cl-Valine in aqueous solution, which is formed rapidly by chlorination of Valine with sodium hypochlorite. A general-base catalyzed process not yet described is reported. The experimental evidence shows two competitive decomposition paths: an unimolecular concerted fragmentation process (k = (1.8 ± 0.1) · 10?4 s?1 at 298 K) and the other one is an E2 elimination process whose importance increases with pH and depends on the nature and the concentration of the bases present in the medium. © 1994 John Wiley & Sons, Inc.  相似文献   
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An experimental study of the thermal decomposition of a β‐hydroxy alkene, 3‐methyl‐3‐buten‐1‐ol, in m‐xylene solution, has been carried out at five different temperatures in the range of 513.15–563.15 K. The temperature dependence of the rate constants for the decomposition of this compound in the corresponding Arrhenius equation is given by ln k (s?1) = (25.65 ± 1.52) ? (17,944 ± 814) (kJ·mol?1T?1. A computational study has been carried out at the M05–2X/6–31+G(d,p) level of theory to calculate the rate constants and the activation parameters by the classical transition state theory. There is a good agreement between the experimental and calculated rate constants and activation Gibbs energies. The bonding characteristics of reactant, transition state, and products have been investigated by the natural bond orbital analysis, which provides the natural atomic charges and the Wiberg bond indices. Based on the results obtained, the mechanism proposed is a one‐step process proceeding through a six‐membered cyclic transition state, being a concerted and slightly asynchronous process. The results have been compared with those obtained previously by us (Struct Chem 2013, 24, 1811–1816) for the thermal decomposition of 3‐buten‐1‐ol, in m‐xylene solution. We can conclude that in the compound studied in this work, 3‐methyl‐3‐buten‐1‐ol, the effect of substitution at position 3 by a weakly activating CH3 group is the stabilization of the transition state formed in the reaction and therefore a small increase in the rate of thermal decomposition.  相似文献   
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Abstract

Due to the wide use of polymers in medicine, researchers are required to solve a very important problem–to understand the interaction between materials of nonphysiological origin and the surrounding biological liquids, and tissues, particularly blood.  相似文献   
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This article deals with the kinetics of decomposition of four isomers: N? Cl-(L)-2-Aminohexanoic acid, N? Cl-(L)-Leucine, N? Cl-(L)-Isoleucine, and N? Cl-(L)-tert-Leucine, in mild acid and basic aqueous solution. An alternative mechanism for this process which takes place through a nitrenium-like ion transition state is proposed. This mechanism is in consonance with the experimental data and with those available from the literature. © 1993 John Wiley & Sons, Inc.  相似文献   
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Santaballa JA  Blanco C  Arce F  Casado J 《Talanta》1985,32(10):931-935
This article describes CONSEL, a least-squares linear-regression program which, when applied to polarographic data, provides estimates of stability constants suitable for priming non-linear optimization programs. The use of CONSEL avoids the need for recourse to traditional graphical methods. The results of its application to three systems are presented.  相似文献   
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The current study provides a way of extraction for both active NSO and WSE from Nigella sativa seeds using 98% methanol. About 1?kg of ground seeds was macerated by 1:2.5 w/v (g/mL) for 72?hours. After rotary evaporation and 7 days of continuous drying and chilling at 50 and 4?°C, NSO and WSE were obtained at the same instant. Solubility tests of 24 solvents and 11 thin layer chromatographic analyses while 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging assay of NSO (73.66) , WSE (33.32) and NSO?+?WSE (78.22) against ascorbic acid (IC50?=?4.28?mg/mL) was performed. WSE was found to be highly soluble in water and 5% NaOH exhibiting the same Rf value of 0.95 for EtOH:DMSO (9:1) against the honey. WSE has revealed more than twofold higher anti-oxidant activity than others. Formulation of WSE with Tualang honey may provide better targeted hydrophilic drug delivery systems.  相似文献   
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高聚合度Ⅱ-型聚磷酸铵的合成   总被引:3,自引:0,他引:3  
傅亚  陈君和  贾云  郭莉平 《合成化学》2005,13(6):610-613
用聚合反应-热处理两段工艺合成了高聚合度的聚磷酸铵(APP)阻燃材料,其结构经XRD,粒度及平均聚合度表征。优化反应条件为:磷酸氢二铵1mol,n(磷酸氢二铵):n(五氧化二磷):n(脲):1.0:1.0:0.3.干燥氨气氛下于290℃反应30min,再经250℃-280℃后处理100min-110min。APP的平均聚合度大于150,粒度小于50μm。  相似文献   
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