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Tarabay J.,CNRS Research on Catalysis and Environment in Lyon | Al-Maksoud W.,CNRS Research on Catalysis and Environment in Lyon | Jaber F.,Laboratoire Danalyse Of Pesticides Et Of Polluants Organiques | Pinel C.,CNRS Research on Catalysis and Environment in Lyon | And 2 more authors.
Applied Catalysis A: General | Year: 2010

The synthesis of diethyl 2-(aryl)vinylphosphonate through direct Heck coupling reaction of the diethyl vinylphosphonate with aryl or heteroaryl halides catalysed by solid materials ([Pd(NH 3) 4]/NaY, Pd/C, PdO/SiO 2) is reported. After optimising the reaction conditions (1.3 mol% [Pd(NH 3) 4]/NaY, DMF, K 2CO 3, 110-140 °C), various aryl and heteroaryl halides were engaged in this reaction leading in all cases good to high yields. Interestingly, when using activated aryl bromides the palladium loading could be lowered to only 0.25 mol%. While highly active when coupling aryl iodides (i.e. only 0.15 mol% required), the PdO/SiO 2 catalyst was found to be inactive when considering aryl bromides. Deep study of this catalytic material revealed that in the case of aryl bromides, absence of in situ reduction of the catalyst precursor prevents the cross-coupling reaction with this latter material. © 2010 Elsevier B.V. All rights reserved. Source


Adraa K.E.,CNRS Surface Science Lab | Timon V.,CNRS Surface Science Lab | Timon V.,Instituto Andaluz Of Ciencias Of La Tierra | Lambert J.-F.,CNRS Surface Science Lab | And 5 more authors.
Journal of Physical Chemistry C | Year: 2012

The intercalation of l-DOPA into the interlayer space of saponite, a 2:1 phyllosilicate, and the nature of host-guest interactions are investigated by a combined experimental and theoretical approach. l-DOPA zwitterions are accommodated vertically in the interlayer region as a bilayer of partially interdigitated species. The hydration state of the nanocomposite as well as the interaction geometry of l-DOPA molecules in the clay interlayer, are determined by periodic DFT calculations and found to be in agreement with experimentally obtained data. New insights into the transport properties for biomolecules in saponite are discussed. © 2012 American Chemical Society. Source


Rifai A.,Ecole Polytechnique - Palaiseau | Rifai A.,Laboratoire Danalyse Of Pesticides Et Of Polluants Organiques | Bourcier S.,Ecole Polytechnique - Palaiseau | Arquier D.,University Paris - Sud | And 3 more authors.
Journal of Mass Spectrometry | Year: 2011

Dinoterb (6-t-butyl-2,4-dinitrophenol), 1, Dinoseb (6-secbutyl-2,4- dinitrophenol), 2, TBP (2-t-butylphenol), 3, and DNP (2,4-dinitrophenol), 4, have been analyzed by electrospray ionization in the negative mode (ESI-N) - tandem mass spectrometry. Nominal laboratory collision energy was varied from zero to 60 eV during the experiments. Apparent fragmentation energies were estimated from a parametric fitting of the collision efficiency curves. In parallel, fragmentation mechanisms of the deprotonated molecules [M-H] - were explored using quantum chemistry modeling at the B3LYP/6-31 + G(d,p) level. A major fragmentation of the [M-H] - ions of Dinoterb and Dinoseb is elimination of an alcohol molecule. This reaction is shown to involve one oxygen atom originating from a nitro group rather than the phenoxide moiety. Eliminations of NO, CH 4 and CH 2 = C(CH 3) 2, i.e. reactions involving significant rearrangements, constitute the major part of the other fragmentation pathways observed from [3-H] - and [4-H] - ions. Copyright © 2011 John Wiley & Sons, Ltd. Source


Rifai A.,Ecole Polytechnique - Palaiseau | Rifai A.,Laboratoire Danalyse Of Pesticides Et Of Polluants Organiques | Bourcier S.,Ecole Polytechnique - Palaiseau | Jaber F.,Laboratoire Danalyse Of Pesticides Et Of Polluants Organiques | Bouchoux G.,Ecole Polytechnique - Palaiseau
International Journal of Mass Spectrometry | Year: 2013

Methamidophos, 1, is examined by tandem mass spectrometry (Q-TOF) under electrospray ionization in the positive ion mode (ESI-P). Variable collision energy MS-MS mass spectra of protonated methamidophos, 1H+, reveal that CH2O, CH3SH, CH3OH and NH3 losses occur with comparable threshold energies. Fragmentations leading to m/z 125, 112, 110, 94, 79 and m/z 64 ions are explained by combinations of 1,2-elimination reactions and isomerizations via 1,3-proton migrations as supported by B3LYP/6-31+G(d) calculations. The behavior of electron ionized methamidophos, 1+, particularly its fragmentations by losses of SCH3 and CH2S, is also explored at the B3LYP/6-31+G(d) level. G4MP2 calculation shows that protonation of 1 occurs preferentially at the oxygen atom of the PO group with a corresponding proton affinity equal to PA(1) = 897 kJ mol-1. Calculated G4MP2 ionization energy and heat of formation of methamidophos are IE(1) = 8.77 eV and ΔfH° 298(1) = -626 kJ mol-1. © 2013 Elsevier B.V. Source

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