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41.
Thomas Mouton Xavier Mercier Maxime Wartel Nathalie Lamoureux Pascale Desgroux 《Applied physics. B, Lasers and optics》2013,112(3):369-379
This paper presents the study we carried out on the formation of soot particles in low-pressure premixed CH4/O2/N2 flames by using Laser-Induced Incandescence (LII). Flames were stabilised at 26.6 kPa (200 torr). Four different equivalence ratios were tested (Φ = 1.95, 205, 2.15 and 2.32), Φ = 1.95 corresponding to the equivalence ratio for which LII signals begin to be measurable along the flame. The evolution of the LII signals with laser fluence (fluence curve), time (temporal decay) and emission wavelength is reported at different heights above the burner. We specifically took advantage of the low-pressure conditions to probe with a good spatial resolution the soot inception zone of the flames. Significant different behaviours of the fluence curves are observed according to the probed region of the flames and Φ. In addition, while the surface growth process is accompanied by an increase in the LII decay-times (indicator of the primary particle diameter) at higher Φ, decay-times become increasingly short at lower Φ reaching a constant value along the flame at Φ = 1.95. These behaviours are consistent with the detection of the smallest incandescent particles in the investigated flames, these particles having experienced very weak surface growth. Flame modelling including soot formation has been implemented in flames Φ = 2.05 and 2.32. Experimental quantitative soot volume fraction profiles were satisfactorily reproduced by adjusting the fraction of reactive soot surface available for reactions. The qualitative variation of the computed soot particle diameter and the relative weight of surface growth versus nucleation were consistent with the experimental observations. 相似文献
42.
Mn-distribution patterns of the calcareous particles collected in the English Channel were investigated. A sub-division of the total Mn amount of the particles into component phases (carbonate, metal oxides, organic matter and alumino-silicates) was achieved. Selected experiments carried out under marine conditions were run in order to demonstrate whether or not certain reactions involving manganese(II) occur and even predominate in English Channel seawaters. An electron spin resonance study was carried out on the Mn chemistry of complex mixtures of heterogeneous fractions like those found in the calcareous particles from the English Channel. Our investigations have shown that: (i) manganese is essentially in the oxidation state II in this marine environment; (ii) particulate Mn is poorly bound to organic compounds and alumino-silicates; and (iii) most of the Mn(II) is strongly adsorbed on the carbonate fraction to give a solid solution of MnxCa1–xCO3. The concentrations of Mn oxides along the French coast are too low to govern the solubility of Mn in these calcareous seawaters. It was therefore suggested that MnCO3-CaCO3 plays a decisive role in that regard. 相似文献
43.
In a systematic study of the sulphonating properties of SO(3)B complexes, we have paid attention to the thiocyanosulphates KSO(3)SCN and NH(4)SO(3)SCN. We have shown conductimetrically that these salts are dissociated and that the ionic salvation is weak in the chosen solvent-sulpholane-which is strongly aprotic in character. We have determined potentiometrically the equilibrium constant K of the reaction MSO(3)SCN measured angle MSCN + SO(3), by means of the electrochemical couple Ag + SO(3)SCN(-) measured angle AgSCN + SO(3) + e(-). The values foun the ammonium and potassium salts are K = 10(-11.5 +/- 0.45) and 10(-9.7 +/- 0.7) respectively. Thiocyanosulphates appear to be stronger than chlorosulphates as sulphonating agents. Therefore SCN(-) is a weaker base than Cl(-) in sulpholane medium. 相似文献
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46.
Zhongrui Chen Maxime Bert Simon Pascal Gabriel Canard Olivier Siri 《Tetrahedron letters》2019,60(38):151024
The transamination reaction of 2,5-diaminobenzoquinonediimine (QDI) with ethylenediamine gave fluorescent 1,2,3,4-tetrahydropyrazino[2,3-g]quinoxaline (1). When the same reaction was carried out with N,N’-bis(aminoethyl)-1,3-propanediamine, a novel cationic quinoxalinium species (2) was isolated, which can be further condensed with p-cyanobenzaldehyde to afford a benzimidazolo-fused quinoxaline dye (3) that is a water-soluble fluorophore in the UV–visible range. 相似文献
47.
Maxime Jarret Victor Turpin Aurlien Tap Jean‐Franois Gallard Cyrille Kouklovsky Erwan Poupon Guillaume Vincent Laurent Evanno 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(29):9966-9970
Reported is the enantioselective total syntheses of mavacuran alkaloids, (+)‐taberdivarine H, (+)‐16‐hydroxymethyl‐pleiocarpamine, and (+)‐16‐epi‐pleiocarpamine, and their postulated biosynthetic precursor 16‐formyl‐pleiocarpamine. This family of monoterpene indole alkaloids is a target of choice since some of its members are subunits of intricate bisindole alkaloids such as bipleiophylline. Inspired by the biosynthetic hypothesis, an oxidative coupling approach from the geissoschizine framework to form the N1?C16 bond was explored. Quaternization of the aliphatic nitrogen center was key to achieving the oxidative coupling induced by KHMDS/I2 as it masks the nucleophilicity of the aliphatic nitrogen center and locks in the required cis conformation. 相似文献
48.
Dr. Marc Devillard Dr. Andreas Ehlers Dr. Maxime A. Siegler Dr. Ir. Jarl Ivar van der Vlugt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3875-3883
Ligands with reactive carbon sites in the periphery of a metal center have emerged as a powerful approach for metal–ligand bond activation. These reactive carbon sites are commonly generated by deprotonation strategies. Carbon–silicon bond cleavage is a potential alternative to access such constructs. Herein, the monodesilylation of bis-silyl-substituted P,N scaffold PNSi2 in the coordination sphere of [RhI(Cl)(CO)( PNSi2 )] ( 1 ) with sodium azide is disclosed. This affords a unique dinucleating anionic κ2-C,N-κ1-P ligand with a carbanionic methine carbon atom directly bound to rhodium as part of a four-membered Rh-N-C-C rhodacycle. This dimer undergoes meta-pyridine C−H activation facilitated by weak bases, which leads to a desymmetrization of the system and provides a σ,π-bridging 3-pyridyl fragment bound to RhI. The facile Si−C cleavage strategy may pave the way to studying the reactivity and functionalization of a variety of κ2-C,N-coordinated pyridine scaffolds for selective transformations. 相似文献
49.
We report on the characterization of an InP/InGaAsP-material-based microdisk resonator optical filter. The originality here is constituted by the use of a localized control electrode that is used for the tuning of the resonance wavelength of the filter via the injection of a driving current. Tuning of the resonance wavelength close to 8 nm has been experimentally achieved for a drive current of 80 mA. 相似文献
50.
Dr. Shaima Hkiri Maxime Steinmetz Prof. Rachel Schurhammer Dr. David Sémeril 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(58):e202201887
The neutral complex dichloro-{diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)-(4-trifluoro-methylphenyl)methyl]phosphonate} (p-cymene)-ruthenium(II) was encapsulated inside a self-assembled hexameric host obtained upon reaction of 2,8,14,20-tetra-undecyl-resorcin[4]arene and water. The formation of an inclusion complex was inferred from a combination of spectral measurements (MS, UV/Vis spectroscopy, 1H and DOSY NMR). The 31P and 19F NMR spectra are consistent with motions of the ruthenium complex inside the self-assembled capsule. Molecular dynamics simulations carried out on the inclusion complex confirmed these intra-cavity movements and highlighted possible supramolecular interactions between the ruthenium first coordination sphere ligands and the inner part (aromatic rings) of the capsule. The embedded ruthenium complex was assessed in the catalytic oxidation (using NaIO4 as oxidant) of mixtures of three arylmethyl alcohols into the corresponding aldehydes. The reaction kinetics were shown to vary as a function of the substrates’ size, with the oxidation rate varying in the order benzylalcohol >4-phenyl-benzylalcohol >9-anthracenemethanol. Control experiments realized in the absence of hexameric capsule did not allow any discrimination between the substrates. 相似文献