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Jia Zhang Florence Vermeire Ruben Van de Vijver Olivier Herbinet Frédérique Battin-Leclerc Marie-Françoise Reyniers Kevin M. Van Geem 《国际化学动力学杂志》2020,52(11):785-795
3-Carene is an important potential biofuel with properties similar to the jet-propellant JP-10. Its thermal decomposition and combustion behavior is to date unknown, which is essential to assess its quality as a fuel. A combined experimental and kinetic modeling study has been conducted to understand the initial decomposition of 3-carene. The pyrolysis of 3-carene was investigated in a jet-stirred quartz reactor at atmospheric pressure, at temperatures varying from 650 to 1050 K, covering the complete conversion range. The decomposition of 3-carene was observed to start around 800 K, and it is almost complete at 970 K. Online gas chromatography shows that primarily aromatics are generated which suggests that 3-carene is not a good fuel candidate. The potential energy surface for the initial decomposition pathways determined by KinBot shows that a hydrogen elimination reaction dominates, giving primarily cara-2,4-diene. Next to this molecular pathway, radical pathways lead to aromatics via ring opening. The kinetic model was automatically generated with Genesys and consists of 2565 species and 9331 reactions. New quantum chemical calculations at the CBS-QB3 level of theory were needed to calculate rate coefficients and thermodynamic properties relevant for the primary decomposition of 3-carene. Both the conversion of 3-carene and the yields of the primary products (ie, benzene and hydrogen gas) are well predicted with this kinetic model. Rate of production analyses shows that the dominant pathways to convert 3-carene are hydrogen elimination reaction and radical chemistry. 相似文献
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Olivier Herbinet Benoit Husson Hervé Le Gall Frédérique Battin-Leclerc 《国际化学动力学杂志》2020,52(12):1006-1021
In the context of better understanding pollutant formation from internal combustion engines, new experimental speciation data were obtained in a high-pressure jet-stirred reactor for the oxidation of three molecules, which are considered in surrogates of diesel fuel, n-heptane, ethylbenzene, and n-butylbenzene. These experiments were performed at pressures up to 10 bar, at temperatures ranging from 500 to 1 100 K, and for a residence time of 2 s. Based on results previously obtained close to the atmospheric pressure for the same molecules, the pressure effect on fuel conversion and product selectivity was discussed. In addition, for the three fuels, the experimental temperature dependence of species mole fractions was compared with simulations using recent literature models with generally a good agreement. For n-heptane, the obtained experimental data, at 10 bar for stoichiometric mixtures, included the temperature dependence of the mole fractions of the reactants and those of 21 products. Interestingly, the formation of species previously identified as C7 diones was found significantly enhanced at 10 bar compared with lower pressures. The oxidation of ethyl- and n-butylbenzenes was investigated at 10 bar for equivalence ratios of 0.5, 1, and 2. The obtained experimental data included the temperature dependence of the mole fractions of the reactants and those of 13 products for the C8 fuels and of 19 products for the C10 one. For ethylbenzene under stoichiometric conditions, the pressure dependence (from 1 to 10 bar) of species mole fraction was also recorded and compared with simulations with more deviations obtained than for temperature dependence. For both aromatic reactants, a flow rate analysis was used to discuss the main pressure influence on product selectivities. 相似文献
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Cyrille Charpentier Jérémy Salaam Dr. Aline Nonat Fabio Carniato Dr. Olivier Jeannin Dr. Isabel Brandariz Dr. David Esteban-Gomez Dr. Carlos Platas-Iglesias Dr. Loïc J. Charbonnière Prof. Mauro Botta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(24):5407-5418
The heptadentate ligand L was shown to form an extremely stable Gd complex at neutral pH with a pGd value of 18.4 at pH 7.4. The X-ray crystal structures of the complexes formed with Gd and Tb displayed two very different coordination behaviors being, respectively, octa- and nonacoordinated. The relaxometric properties of the Gd complex were studied by field-dependent relaxivity measurements at various temperatures and by 17O NMR spectroscopy. The pH-dependence of the longitudinal relaxivity profile indicated large changes around neutral pH leading to a very large value of 10.1 mm −1⋅s−1 (60 MHz, 298 K) at pH 4.7. The changes were attributed to an increase of the hydration number from one water molecule in basic conditions to two at acidic pH. A similar trend was observed for the luminescence of the Eu complex, confirming the change in hydration state. DOSY experiments were performed on the Lu analogue, pointing to the absence of dimers in solution in the considered pH range. A breathing mode of the complex was postulated, which was further supported by 1H and 31P NMR spectroscopy of the Yb complex at varying pH and was finally modeled by DFT calculations. 相似文献
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Tania Merhi Alban Jonchère Dr. Luc Girard Dr. Olivier Diat Miquel Nuez Prof. Clara Viñas Dr. Pierre Bauduin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(61):13935-13947
Metalla-bis-dicarbollides, such as the cobalta-bis-dicarbollide (COSAN) anion [Co(C2B9H11)2]−, have attracted much attention in biology but a deep understanding of their interactions with cell components is still missing. For this purpose, we studied the interactions of COSAN with the glucose moiety, which is ubiquitous at biological interfaces. Octyl-glucopyranoside surfactant (C8G1) was chosen as a model as it self-assembles in water and creates a hydrated glucose-covered interface. At low COSAN content and below the critical micellar concentration (CMC) of C8G1, COSAN binds to C8G1 monomers through the hydrophobic effect. Above the CMC of C8G1, COSAN adsorbs onto C8G1 micelles through the superchaotropic effect. At high COSAN concentrations, COSAN disrupts C8G1 micelles and the assemblies become similar to COSAN micelles but with a small amount of solubilized C8G1. Therefore, COSAN binds in a versatile way to C8G1 through either the hydrophobic or superchaotropic effect depending on their relative concentrations. 相似文献
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Pierre Thesmar Seemon Coomar Dr. Alessandro Prescimone Prof. Dr. Daniel Häussinger Prof. Dr. Dennis Gillingham Prof. Dr. Olivier Baudoin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(66):15298-15312
This article provides a detailed report of our efforts to synthesize the dithiodiketopiperazine (DTP) natural products (−)-epicoccin G and (−)-rostratin A using a double C(sp3)−H activation strategy. The strategy's viability was first established on a model system lacking the C8/C8’ alcohols. Then, an efficient stereoselective route including an organocatalytic epoxidation was secured to access a key bis-triflate substrate. This bis-triflate served as the functional handles for the key transformation of the synthesis: a double C(sp3)−H activation. The successful double activation opened access to a common intermediate for both natural products in high overall yield and on a multigram scale. After several unsuccessful attempts, this intermediate was efficiently converted to (−)-epicoccin G and to the more challenging (−)-rostratin A via suitable oxidation/reduction and protecting group sequences, and via a final sulfuration that occurred in good yield and high diastereoselectivity. These efforts culminated in the synthesis of (−)-epicoccin G and (−)-rostratin A in high overall yields (19.6 % over 14 steps and 12.7 % over 17 steps, respectively), with the latter being obtained on a 500 mg scale. Toxicity assessments of these natural products and several analogues (including the newly synthesized epicoccin K) in the leukemia cell line K562 confirmed the importance of the disulfide bridge for activity and identified dianhydrorostratin A as a 20x more potent analogue. 相似文献
10.
Thomas Mikosch Mohsen Rezapour Olivier Wintenberger 《Stochastic Processes and their Applications》2019,129(11):4638-4662
In this paper we consider a stochastic model of perpetuity-type. In contrast to the classical affine perpetuity model of Kesten (1973) and Goldie (1991) all discount factors in the model are mutually independent. We prove that the tails of the distribution of this model are regularly varying both in the univariate and multivariate cases. Due to the additional randomness in the model the tails are not pure power laws as in the Kesten–Goldie setting but involve a logarithmic term. 相似文献