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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?1)·T?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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Through SiP bond cleavage, the reaction of P7(SiMe3)3 with one equivalent of KOtBu or LiOtBu afforded different isomers of the heptaphosphanide anion [P7(SiMe3)2]−. With LiOtBu, concomitant inversion at an equatorial (silylated) phosphorus atom occurred and the Cs symmetric isomer characterized by a mirror plane formed. With KOtBu, inversion did not occur and the resulting asymmetric anion with C1 symmetry formed. With NaOtBu, a mixture of both isomers was obtained. The symmetries and structures of the anions were elucidated with 31P{1H} and 29Si{1H} NMR spectroscopy, and relative stabilities were calculated employing the B3LYP/6-31+G* method.The reaction of KP7(SiMe3)2 or LiP7(SiMe3)2 with 1,2-dichlorotetramethyldisilane led to (SiMe3)2P7SiMe2SiMe2P7(SiMe3)2, a molecule composed of two P7-cages connected by a disilane bridge. It can also be obtained through silyl exchange using P7(SiMe3)3 and ClMe2SiSiMe2Cl. The compound was characterized with 31P and 29Si-NMR spectroscopy and elemental analysis. Treatment of P7(SiMe3)3 with HypCl (Hyp = hypersilyl = Si(SiMe3)3) in DME led to the quantitative formation of Hyp2P7SiMe3. Single crystal X-ray diffraction as well as 31P and 29Si-NMR spectroscopy proves the presence of a heteroleptically substituted heptaphosphane cage.Quantum chemical HF and B3LYP/6-31G* calculations of equilibrium structures for the two possible isomers of P7(SiMe3)3 (sym and asym) reveal that asym is destabilized by about 30-40 kJ mol−1, which explains why its formation could not be observed. The phosphorus inversion barrier for the sym → asym transition is calculated as 60-70 kJ mol−1. 相似文献
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Z.M. Babar Wan Mohd Azizi Solachuddin JA Ichwan Qamar Uddin Ahmed Abul Kalam Azad Imranul Mawa 《Natural product research》2019,33(15):2266-2270
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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We report on a simple method with a high spectral and spatial resolution for mapping variations in the cavity resonance of a plano-planar broad-area laser based on frequency-selective feedback. The demonstration experiment uses a vertical-cavity surface-emitting-laser (VCSEL), in which growth induced inhomogeneities are of particular importance. It relies only on a standalone laser with a narrow-bandwidth passive filter avoiding the need for an expensive tunable laser or high-resolution spectrometer. 相似文献
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