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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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Glinec Y Faure J Dain LL Darbon S Hosokai T Santos JJ Lefebvre E Rousseau JP Burgy F Mercier B Malka V 《Physical review letters》2005,94(2):025003
An electron beam from a laser-plasma accelerator is converted into a gamma-ray source using bremsstrahlung radiation in a dense material. The gamma-ray beam has a pointlike source size because it is generated by a high quality electron beam with a small source size and a low divergence. Using this gamma-ray source, the radiography of complex and dense objects with submillimeter resolution is performed. It is the first evidence of a gamma-ray source size of a few hundreds micrometers produced with laser-driven accelerators. This size is consistent with results from Monte Carlo simulations. 相似文献
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Christopher M. Leavitt Jos Oomens Ryan P. Dain Jeffrey Steill Gary S. Groenewold Michael J. Van Stipdonk 《Journal of the American Society for Mass Spectrometry》2009,20(5):772-782
Anionic group II metal nitrate clusters of the formula [M2(NO3)5]−, where M2 = Mg2, MgCa, Ca2, and Sr2, are investigated by infrared multiple photon dissociation (IRMPD) spectroscopy to obtain vibrational spectra in the mid-IR
region. The IR spectra are dominated by the symmetric and the antisymmetric nitrate stretches, with the latter split into
high and low-frequency components due to the distortion of nitrate anion symmetry by interactions with the cation. Density
functional theory (DFT) is used to predict geometries and vibrational spectra for comparison to the experimental spectra.
Calculations yield two stable isomers: the first one contains two terminal nitrate anions on each cation and a single bridging
nitrate (“mono-bridging”), while the second structure features a single terminal nitrate on each cation with three bridging
nitrate ligands (“tri-bridging”). The tri-bridging isomer is calculated to be lower in energy than the mono-bridging one for
all species. Theoretical spectra of the tri-bridging structure provide a better qualitative match to the experimental infrared
spectra of [Mg2(NO3)5]− and [MgCa(NO3)5]−. However, the profile of the low-frequency ν
3 band for the Mg2 complex suggests a third possible isomer not predicted by theory. The IRMPD spectra of the Ca2 and Sr2 complexes are better reconciled by a weighted summation of the spectra of both isomers suggesting that a mixture of structures
is present. 相似文献
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Gary S. Groenewold Christopher M. Leavitt Ryan P. Dain Jos Oomens Jeffrey D. Steill Michael J. van Stipdonk 《Rapid communications in mass spectrometry : RCM》2009,23(17):2706-2710
Tandem mass spectrometry and wavelength‐selective infrared photodissociation were used to generate an infrared spectrum of gas‐phase triethylphosphate cationized by attachment of K+. Prominent absorptions were observed in the region of 900 to 1300 cm?1 that are characteristic of phosphate P?O and P? O? R stretches. The relative positions and intensities of the IR absorptions were reproduced well by density functional theory (DFT) calculations performed using the B3LYP functional and the 6‐31+G(d), 6‐311+G(d,p) and 6‐311++G(3df,2pd) basis sets. Because of good correspondence between experiment and theory for the cation, DFT was then used to generate a theoretical spectrum for neutral triethylphosphate, which in turn accurately reproduces the IR spectrum of the neat liquid when solvent effects are included in the calculations. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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