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81.
Bertrand Schweitzer‐Chaput Joachim Demaerel Hauke Engler Dr. Martin Klussmann 《Angewandte Chemie (International ed. in English)》2014,53(33):8737-8740
Based on a mechanistic study, we have discovered a Brønsted acid catalyzed formation of ketone radicals. This is believed to proceed via thermally labile alkenyl peroxides formed in situ from ketones and hydroperoxides. The discovery could be utilized to develop a multicomponent radical addition of unactivated ketones and tert‐butyl hydroperoxide to olefins. The resulting γ‐peroxyketones are synthetically useful intermediates that can be further transformed into 1,4‐diketones, homoaldol products, and alkyl ketones. A one‐pot reaction yielding a pharmaceutically active pyrrole is also described. 相似文献
82.
Luke Green Keith Livingstone Dr. Sophie Bertrand Dr. Simon Peace Dr. Craig Jamieson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(65):14866-14870
A range of 1,3,4-oxadiazoles have been synthesized using a UV-B activated flow approach starting from carboxylic acids and 5-substituted tetrazoles. The application of UV light represents an attractive alternative to the traditional thermolytic approach and has demonstrated comparable efficiency and versatility, with a diverse substrate scope, including the incorporation of highly substituted amino acids. 相似文献
83.
Victor de Seauve Marie‐Anglique Languille Mathieu Kociak Stphanie Belin James Ablett Christine Andraud Odile Stphan Jean‐Pascal Rueff Emiliano Fonda Bertrand Lavdrine 《Angewandte Chemie (International ed. in English)》2020,59(23):9113-9119
The first colour photographs were created by a process introduced by Edmond Becquerel in 1848. The nature of these photochromatic images colours motivated a debate between scientists during the XIXth century, which is still not settled. We present the results of chemical analysis (EDX, HAXPES and EXAFS) and morphology studies (SEM, STEM) aiming at explaining the optical properties of the photochromatic images (UV‐visible spectroscopy and low loss EELS). We rule out the two hypotheses (pigment and interferences) that have prevailed since 1848, respectively based on variations in the oxidation degree of the compound forming the sensitized layer and periodically spaced photolytic silver planes. A study of the silver nanoparticles dispersions contained in the coloured layers showed specific localizations and sizes distributions of the nanoparticles for each colour. These results allow us to formulate a plasmonic hypothesis on the origin of the photochromatic images colours. 相似文献
84.
Effect of salinity on petroleum biodegradation 总被引:1,自引:0,他引:1
G. Mille M. Almallah M. Bianchi F. van Wambeke J. C. Bertrand 《Fresenius' Journal of Analytical Chemistry》1991,339(10):788-791
Summary The biodegradation of Ashtart crude oil by a mixed bacterial community (EH1) isolated from a marine sediment was investigated in varying concentration of sodium chloride (0 to 2 mol/l). Each fraction of Ashtart crude oil was biodegraded after a 30 day incubation period for a NaCl concentration equivalent to the one of seawater (0.4 mol/l). Saturates were more readily degraded than aromatics. The amount of oil degraded increased initially with increasing salt concentrations to a maximum level for 0.4 mol/l NaCl concentration. Thereafter the amount of oil degraded decreased with increasing salt concentrations. The polar fraction increased for the 0.4 to 1.4 mol/l NaCl concentration range. Asphaltenes were only slightly degraded (10%) for a NaCl concentration equivalent to the one of seawater (0.4 mol/l). NaCl concentrations seemed to affect the relative biodegradation of pristane and phytane. GC, UV fluorescence and FTIR techniques were used to study the evolution of each fraction of Ashtart crude oil. 相似文献
85.
Bernard Lavielle Bertrand Thomas Eric Gilabert Gregory Canchel Denis Horlait Sylvain Topin Fabien Pointurier Christophe Moulin 《Journal of mass spectrometry : JMS》2016,51(10):908-913
A double focusing sector field mass filter used in Nier–Johnson geometry has been built in order to perform Kr isotope enrichment for 81Kr and 85Kr isotopes. The principle consists in implanting Kr+ ions accelerated at 7 keV in Al foils after separation using the magnetic sector. A specific ion source has been designed capable of generating high Kr+ ion beams (>0.5 μA) to transfer into the collecting Al foils in 3 to 5 h significant fractions of large Kr samples (1015 to 1016 atoms) initially introduced in the instrument. Implanted Kr isotopes can be further selectively released from the Al foil by surface ablation using an infrared laser beam. Implantation yields and enrichment factors are measured using a conventional mass spectrometer. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
86.
Dr. David Martin Dr. Nicolas Lassauque Florian Steinmann Gerald Manuel Prof. Guy Bertrand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(44):14895-14901
Experimental and computational investigations of anti‐Bredt amidinium salts are presented. Calculations show that the pyramidalization of an amino group can significantly destabilize the formal carbocation center of amidiniums, due to the decreased π donation. In some cases, the unfavorable ‐I effect of nitrogen surpasses its beneficial +M effect, and amidiniums become less stable than iminiums. It is shown that although 1‐aza‐3‐azonia[3.3.1]bicyclo‐non‐2‐enes can be isolated, they feature a nonclassical reactivity, which is more typical for iminium than amidinium salts, such as pronounced electrophilicity and azomethineylide instead of carbene formation. 相似文献
87.
A. Wnuk M. Kaczkan R. Piramidowicz R. Mahiou G. Bertrand M.-F. Joubert 《辐射效应与固体损伤》2013,168(1-6):469-473
The dynamics of up-conversion, green emission under excitation at different infra-red wavelength in Ho3? doped ZBLAN fiber is reported. Under infrared, 890 nm quasi cw pumping the complicated temporal behavior of the up-conversion signal is strongly influenced by the intermediate 5I5 state cross relaxation. The mechanisms of the observed up-conversion processes are proposed and the time evolution of the 5S2 population is described by the rate equation model. Parameters of the model are determined and numerical simulations of the excited state dynamics are performed. 相似文献
88.
Literature methods for synthesis of small and medium size monocyclic hydroxamic acids are reviewed, covering the last 30 years. 相似文献
89.
N‐(2‐Ethylhexyl)carbazole: A New Fluorophore Highly Suitable as a Monomolecular Liquid Scintillator
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Eva Montbarbon Dr. Fabien Sguerra Dr. Guillaume H. V. Bertrand Élodie Magnier Dr. Romain Coulon Dr. Robert B. Pansu Dr. Matthieu Hamel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):12074-12080
The synthesis, photophysical properties, and applications in scintillation counting of N‐(2‐ethylhexyl)carbazole (EHCz) are reported. This molecule displays all of the required characteristics for an efficient liquid scintillator (emission wavelength, scintillation yield), and can be used without any extra fluorophores. Thus, its scintillation properties are discussed, as well as its fast neutron/gamma discrimination. For the latter application, the material is compared with the traditional liquid scintillator BC‐501 A, and other liquid fluorescent molecules classically used as scintillation solvents, such as xylene, pseudocumene (PC), linear alkylbenzenes (LAB), diisopropylnaphthalene (DIN), 1‐methylnaphthalene (1‐MeNapht), and 4‐isopropylbiphenyl (iPrBiph). For the first time, an excimeric form of a molecule has been advantageously used in scintillation counting. A moderate discrimination between fast neutrons and gamma rays was observed in bulk EHCz, with an apparent neutron/gamma discrimination potential half of that of BC‐501 A. 相似文献
90.
Ahlem Bouhlel Christophe Curti Michèle P. Bertrand Patrice Vanelle 《Tetrahedron》2012,68(18):3596-3604
An easily reproducible protocol allowing inter- or intramolecular spirocyclization on β-dicarbonyl structures is described. This methodology could afford a wide variety of spirocyclic pharmacophores. As examples, highly substituted spirobenzophenanthridin-6(5H)-ones and spirolactones were synthesized. These scaffolds could be used for the design of many compounds exhibiting biological activities. 相似文献