Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry最新文献

Adsorption of aqueous solution of two amino acids – phenylalanine (Phe) and tyrosine (Tyr) – on powdered activated carbon (PAC) has been studied in the presence of linear or branched alcohols. Methanol has no influence on the adsorption. For the other alcohols, the adsorption decreases when the alcohol chain gets longer, from ethanol to 1-propanol, up to 85 %. Alcohol branching reduces this phenomenon. Adsorption kinetics have been tested according two models, allowing good representation of results and determination of kinetic constants.

The addition of carbon disulfide to 3(5)-N-〚methyl (ethyl)-2-aminophenyl amino-5(3)-phenylpyrazole 3 (4) afforded 10-methyl (ethyl)-3-phenylpyrazolo〚4,3-c〛 〚1,5〛 benzodiazepine-4-thione 7 (8). These compounds reacted with alkyl halides and acetylhydrazide or benzoylhydrazide, to afford new heterocyclic systems: pyrazolo 〚4,3-c〛 triazolo〚4,3-a〛-1,5-benzodiazepines 15–18. Biological properties of compounds 8, 9, 16 and 17 have been evaluated.

The first synthesis of 1,3-diethyl-2,2-dimethoxymethylcyclohexane starting from the easily available methyl 6-ethyl-2-oxocyclohexanecarboxylate via a process involving the building up of a fourfold carbon by a regiospecific alkylation of a silyl enol ether and the introduction of the ethyl substituent by a carbanionic approach is described. The behaviour of 1,3-diethyl-2,2-dimethoxymethylcyclohexane as external electron donor in high activity supported Ziegler–Natta catalyst is studied. The results presented show that this new donor allows the synthesis of polypropylene with a good isotacticity.

Fluorescence spectroscopy is widely used as a tool for elucidating the structure and dynamics of the micellar medium. A prerequisite commonly encountered for quantitative approaches is that the fluorophore resides exclusively in the micellar phase. Providing the fluorophore with a long alkyl chain may appear advantageous with regard to fixing the probe into the micelle. The present work was aimed at determining which are the consequences of this process from a spectroscopic viewpoint. The nitrobenzoxadiazolyl (NBD) moiety, which leads to well known fluorescent probes, was directly grafted on three fatty amines, the chain length of which varied from 8 to 18 carbon atoms. The spectroscopic properties of these NBD derivatives were investigated in three different micellar media: SDS, CTAB and TX100. The dyes were incorporated into micelles, where they were located in the interfacial region, whatever the chain length. When the dyes were previously dissolved in ethanol, and subsequently placed in the presence of the surfactant solution, complete solubilization was obtained. However, when the surfactant solution was used to dissolve directly a thin film of dye, a certain amount of dye remained non-incorporated and formed microcrystals, whose quantity and size increased with chain length. These microcrystals were mainly detected by UV/Vis-absorption and fluorescence microscopy. They induced drastic errors in the determination of fluorescence quantum yields, although they hardly interfered with other steady-state measurements and with dynamical fluorescence measurements. In conclusion, it appeared that for a small, non-ionic fluorophore such as NBD, the presence of a long alkyl chain is not an advantage. It slows down the incorporation process, unless some alcohol is introduced in the medium. Short-chain probes are therefore best suited for the study of the micellar medium.

By the electrocrystallization technique, it has been possible to synthesize a new charge transfer salt, associating the organic anion ABTS^2–, the radical anion ABTS^– (ABTS is the commercial name of the diammonium salt of the 2-2’ azinobis–3 ethyl benzothiazoline sulfonate), and the inorganic cation La³⁺. From single crystal X-ray diffraction data, the crystal structure was solved at 200 K. La₃(ABTS)₅(H₂O)₃₁ belongs to the triclinic symmetry space group$P\overline{1}$ with the cell parameters: a = 18.342(4) Å, b = 17.720 (4) Å, c = 20.394(4) Å, α = 87.97(3)°, β = 79.08(3)°, γ = 85.21(3)°, V = 6 850(2) Å³ and Z = 2. The crystalline network reveals a two-dimensional character based on an alternation of organic and inorganic layers. A valence bond calculation corresponds to a lanthanum in a (+III) oxidation state. This compound is a mixed anionic valence salt, and in accordance with the charge equilibrium, its formulation must be written (La³⁺)₃(ABTS^2–)₄(ABTS^•–)₁(H₂O)₃₁.

New 1,5-benzothiazepinone derivatives have been synthesized. The cycloaddition of benzylazide with 5-propargyl-1,5-benzothiazepinone 7 gave compounds 9 and 10. The 1,5-benzothiazepinone 8 reacts with hydrazine to give 1,5-benzothiazepinone 11, which gave in hot acetic acid compound 12. The reaction of 3-chloro-1,5-benzothiazepinones 13, 14 or 15 with nucleophiles in DMF afforded the 2-benzylidenebenzothiazin-3-ones 16 and 17. The tosylate 18 gave the 1,5-benzothiazepinone 19 by reaction with N₃TMS in the presence of CsF in DMF.

In this paper, we describe the synthesis of new quinoxalines conjugated to different heterocycles that are susceptible to possess various pharmacological and biological activities, utilizing the 1-allyl(propargyl)-3-(ethoxycarbonylmethylene)-2-oxoquinoxaline as starting material.

Comparison of the crystal structures of Cu(OH)_2(s) and γ-FeO(OH)_(s) shows a structural analogy between both solid phases, despite the difference of formulas. This analogy is related to similar connection modes of the polyhedra, which give rise to two-dimensional structures composed of wavy sheets. Lepidocrocite, γ-FeO(OH)_(s), is obtained from divalent iron hydroxide Fe(OH)_2(s), which exhibits also a two-dimensional framework of brucite type. We propose a mechanism for this reaction, which is probably topotactic. The resulting lepidocrocite structural type allows strong deformations of the octahedral cationic coordination, contrarily to the brucite type. Deformations can be due to the loss of hydrogen atoms in γ-FeO(OH)_(s) or to the strong Jahn–Teller effect that affects divalent copper in Cu(OH)_2(s). If copper hydroxide cannot be isostructural with brucite as it is for Fe(OH)_2(s), an analogy exists with lepidocrocite, even if copper has a pentahedral surrounding, different of that of trivalent iron, which is octahedral. In both crystal structures, one oxygen atom has a peculiar surrounding composed of only two cations and one hydrogen atom. This feature explains probably the low stability of this structural type.

Materials have been obtained by decomposition of liquid benzene, owing to the acoustic shock wave induced by the stimulated Brillouin and Raman scatterings excited by a pulsed laser beam 〚1〛. First, amorphous carbon containing particles of graphite and chaoite have been characterized by X-ray diffraction; second, after distillation of the treated benzene and heating under vacuum, a solid residue with a yellowish colour is obtained and characterized by means of X-ray diffraction, mass spectrometry, and infrared, visible and ultraviolet spectroscopies. In this last material, there are several constituents: in a main part, monohydrogenated benzene cycles, along with compounds of naphtalene type, and, in a small part, polycyclic aromatic hydrocarbons.

The carbon dough electrode with incorporated electrolyte has been used to analyse the electrochemical behaviour of ferrocene, tetracene and perylene in phosphoric acid media 0.1 to 14.8 M. The cyclic voltammetry results obtained for ferrocene with the carbon dough electrode corroborate with polarographic data. Voltamperometric study of the aromatic hydrocarbon oxidation Ar such that of perylene and tetracene on the carbon dough electrode has allowed to establish the normal potential of the corresponding oxido-reducing systems. The existence of the four oxidation states: Ar, Ar⁺, ArH⁺ and Ar²⁺ at different concentrations of phosphoric acid is specified. The results of this study can be used to establish correlations between some of concentrated solution properties of different acids.