Synthese et cyclisation electrophile de la bromhydrine de l'acide homogeranique

A new synthesis of 5-bromohexahydro-4,4,7a-trimethyl-2($\text{3H}$)-Benzofuranone (3aα,5β,7aβ)($\text{1}$) was achieved by electrophilic cyclization of the bromohydrin issued from pure homogeranic acid.     

Synthese de l'acide β fluoroacrylique (fluoro-3 propenoique)

Regioselective Bayer-Villiger oxidation of 2-chloro-2-fluoroethyl-isopropyl ketone ($\text{1}$) gives isopropyl-3-chloro-3 fluoropropionate ($\text{2}$). The dehalogenation of ester ($\text{2}$) with trimethylamine gives isopropyl-3-fluoropropenoate ($\text{3}$). Ester cleavage by trimethylsilyl iodide, in the presence of cyclohexene oxide, gives $\text{trans}$-3-fluoropropenoic acid ($\text{4}$).     

Reaction de l'acetylene dicarboxylate d'ethyle avec l'oxo-6 (2H) cyclohepta (c) pyrrole ; mecanismes de formation des adduits

The cycloaddition reactions of 6-oxo (2H) cyclohepta (c) pyrroles $\text{4a, b and c}$ with diethyl acetylene dicarboxylate an electron-deficient dienophile of relatively low LUMO energy level, afford the 1:2 adducts $\text{5a, b}{}_1\text{-b}{}_2\text{and c}$ respectively The kinetics of the reactions, investigated By ¹H NMR spectroscopy, have allowed to precise the mechanism of the addition In particular, new-intermediates, 1:2' adducts $\text{6b and c}$ have been observed and isolated for the compound $\text{6c}$.     

Induction asymetrique lors de l'addition de Michael d'un ester α-sulfinyle chiral

During the Michael addition of chiral α-sulfinyl eser (+) $\text{1}$$\text{R}$ on αβ-unsaturated esters, an extent of 24% of asymmetric induction was observed. It is shown that the addition products can be transformed into optically active δ-lactones.     

Etude cristallographique de l'arsénotellurure de zirconium quadratique

Single crystals of zirconium arsenotelluride (PbFCl type) have been prepared by direct synthesis from the elements. Chemical analysis gives: $\text{As}\text{Zr}\text{= 1.43 ± 0.02}$ and $\text{Te}\text{Zr}\text{= 0.46 ± 0.01}$, in atoms. Lattice constants are: a = 3.82 ± 0.01 Å and c = 8.17 ± 0.02Å. Experimental density is equal to 7.14 ± 0.05. Unit cell thus contains Zr_2.00As_2.86Te_0.92. The structure has been solved with 227 reflections of a single crystal recorded at room temperature. The final R factor is 0.081, excluding zero reflections. Part of the arsenic atoms fills a site and the remainder is located in a second site, the occupation of which is completed by a part of zirconium atoms. The third site is occupied, but not filled, by the tellurium atoms and the remainder of zirconium atoms.     

Reactivite ambidente de l'anion imidazolate vis-a-vis d'un electrophile aromatique

The reaction of 1,3,5-trinitrobenzene (TNB) with imidazolide ion (Im^-) provides the first example of the ambifunctional nucleophilic reactivity of this anion towards an aromatic electrophile. The N-adduct $\text{1}$ is formed under kinetic control but the C-adduct $\text{2}$ is the thermodynamically stable product. The N,C-diadduct $\text{3}$ is also observed.     

Structure cristalline et expansion thermique de l'iodure de nickel hexahydrate

The structure of NiI₂, 6 H₂O has been determined by X-ray diffraction techniques. The dimensions of the hexagonal unit cell are: a = 7.638 ± 0.005 Å and c = 4.876 ± 0.005 Å, with Z = 1. The space group is $\text{P}\text{3}\text{m1}$. The structure was deduced from Patterson and Fourier syntheses and refined by least-squares method to a final R value of 0.09. It is almost a layer structure, each layer is composed by n complex ions [Ni(H₂O)₆]²⁺ surrounded by 2 n ions I^?; this is in agreement with the good cleavage of crystals and with the marked anisotropy in the thermal expansion. But the structure may also be regarded as a derivation of NiAs structure, with only $\text{1}\text{8}$ of octahedral holes occupied. A structural classification of compounds MX₂, 6 H₂O is proposed.     

Influence des associations moleculaires sur la copolymerisation de l'acide acrylique avec l'acide methacrylique et avec l'acrylate de methyle

The copolymerization of acrylic acid with methacrylic acid in bulk is investigated at 40 and 60°. It is confirmed that a “matrix effect” occurs only for high contents of acrylic acid. The critical concentration beyond which the matrix effect disappears is shifted towards lower acrylic acid contents for higher temperatures. The copolymer composition is independent of temperature. The copolymerization of acrylic acid with methyl acrylate is investigated in a mixture which determines an “exaltation of the matrix effect” in the homopolymerization of acrylic acid (molar fractions: m_Monomers = 0.34; m_n-Hexane = 0.52; m_Methanol = 0.14). The resulting copolymers are found to contain a much larger fraction of acrylic acid residues than the copolymers formed in bulk or in toluene or DMF solutions.     

Contribution à l'étude structurale de la wüstite solide de haute température

The structure of wüstite Fe_1?zO is studied by neutron diffraction on one polycrystalline sample under equilibrium conditions at high temperature. The mean isotrope temperature factor B is expressed as a sum of two parts, B_Th and B_St, which vary linearly with a single parameter, respectively temperature and z. A classification is established for clusters ($\text{m}\text{n}$) settled from m vacancies in octahedral sites and n Fe^III ions in interstitial sites. Sixteen values have been experimentally determined for the vacancies to interstitials ratio $\text{? =}\text{(z + t)}\text{t}\text{=}\text{m}\text{n}$. A constant value of ?, which is lower than 3, is observed. This result characterizes the short-range order. It eliminates several possibilities of clusters like those obeying the relation $\text{? =}\text{(1 + 3n)}\text{n}$. Other clusters, namely ($\text{16}\text{6}$) or ($\text{40}\text{14}$), might agree. The ($\text{8}\text{3}$) and ($\text{9}\text{4}$) clusters obtained from ($\text{4}\text{1}$) clusters joined by an edge would be the more likely. An analysis of diffuse scattering eliminates the hypothesis of large domains with inverse spinel structure. The structural differences between the three varieties W₁, W₂ and W₃ would not be found in a structural change of clusters.     

Alcoylation par l'iodure de butyle,de l'enolate de tetrabutylammonium de l'acetylacetone; nature de l'entite reagissante

The alkylation of tetrabutylammonium acetylacetonate with butyl iodide was studied in order to specify the nature of the reactive anionic species during the nucleophilic reaction of an ambident anion, under similar conditions to those of phase transfer catalysis. The C/O alkylation ratio changes with neither the solvents nor the enolate concentration; however k_obs, varies with the solvent but does not depend on the énolate concentration. The results and spectrophotometric UV data show that only one reactive species, the ion-pair, is involved.     

Alkylation de l'acetylacetate de methyle par le α(p-nitrophenyl)-ethanol chiral par deshydratation intermoleculaire

Mitsunobu's method of acetoacetic ester alkylation by $\text{p}$-nitrophenyl-ethanol avoid the S_RN1 reaction and is well appropriate for the correlation of absolute configuration and $\text{ee}$ of the O and C alkylation products.     

Microdosage colorimétrique de l'acide periodique par l'acide 2,2'-azino-di(3-ethylbenzothiazole-6-sulfonique)

Periodic acid oxidizes 2,2'-azino-di-(3-ethylbenzothiazole-6-sulfonic acid) in suitable media, to form a compound which absorbs strongly at 420 nm. The reaction provides a very simple spectrophotometric determination of periodate in the range 0.02–0.1 μM. The application of the method to the analysis of sorbitol and mannitol shows its accuracy and precision.     

Polymerisation radiochimique de l'acetaldehyde en phase solide

The radiation induced solid-state polymerization and post-polymerization of crystalline acetaldehyde were studied in a diathermic calorimeter by measuring the heat evolution during polymerization. The heat of melting of crystalline acetaldehyde was found to be 1,4 ± 0,07 kcal mol^?1 and the heat of polymerization 2,5 ± 0,5 kcal mol^?1 at 80–150°K. Under isothermal conditions the rate of the solid state polymerization of acetaldehyde increased with irradiation time up to a maximum and thereafter it decreased. This phenomenon is connected with an increase of the concentration of active centres during irradiation. The propagation rate constant is $\text{k}{}_{\mathrm{p}}\text{? 5 × 10}{}^{\mathrm{?4}}\text{exp(?11,000/RT) cm}{}^3\text{sec}{}^{\mathrm{?1}}$ at 130–140°K and the average time of addition of one monomer unit is 10^?1–10^?2 sec.     

Versatilité de la réactivité de l' acétylènedicarbaldéhyde et d'aldéhydes α-acétyléniques à l'égard des diènes conjugués cycliques et hétérocycliques en milieu acide.

Formic solutions of ADCA react with cyclic and heterocyclic conjugated dienes affording the Diels-Alder $\text{1}$ or pseudo-Michael $\text{2}$ adducts depending on the nature of the diene. Generalisation to RCCCHO and furan shows a similar behaviour (RCO₂,Et, H) and a third possible pathway (electr. subst. of CO on α of furan,RAr, Alk); mechanisms are discussed.     

Isolement de l'acide 3-amino 12-methyl tetradecanoique et de l'acide 3-amino 12-methyl tridecanoique a partir de l'iturine,antibiotique de Bacillus subtilis

lturin, a peptide antibiotic from Bacillus subtilis, was separated into three iturins: A, B, C by thin-layer chromatography. Iturin A, which has an antifungal activity, contains Asp, Glu, Tyr, Ser, Pro in a molar ratio 3:1:1:1:1 and a lipid moiety AL. The latter was shown to be a mixture of C₁₄ (40%) and C₁₅, (60%) amino-acids. The structure of these was determined by combined gas chromatography-mass spectrometry of the N-acetylmethyl esters. Strong peaks at m/e = 144 and m/e = 102 indicate a β-amino group. Identification of acetone and methylethylketone after chromic acid oxidation indicates an iso and anteiso structure. After comparison of the natural amino-acids with synthetic 3-amino pentadecanoic acid it is concluded that the lipid AL is a mixture of 3-amino 12- methyltetradecanoic acid and 3-amino 12-methyltridecanoic acid.     

Action des sulfonyloxaziridines sur une imine. Obtention d'une nitrone par transfert regioselectif de l'oxygene sur l'azote

A pyrrolinic imine has been found to react concurrently with the nitrogen or the oxygen of a $\text{N}$-sulfonyl oxaziridine leading to a N-sulfonyl diaziridine and a nitrone respectively. By contrast an oxaziridine is obtained with a peracid. A possible relation between the regioselectivity of the oxygen transfer and the nature of the reagent is outlined.     

Rearrangement de la catharine en milieu acide: action de l'acide trifluoroacetique

Cleavage of catharine 1 by trifluoroacetic acid led to a pentacyclic product formed by rearrangement of the ibogane moiety with participation of the enamide function. The N-formyl group of compound 5, obtained after NaBH₃CN reduction, was hydrolyzed leading to a hexacyclic derivative, the structure of which was established by X-ray analysis.     

Dosages Polarographiques du Cobalt et du fer a l'aide de nouvelles solutions de,base au trilon

After stressing the necessity of finding new base solutions for use in polarography, the authors show that Trilon B strongly displaces the reduction potentials of numerous elements.Owing to its ready transformation to the trivalent state cobalt can be determined without preliminary separation, in presence of an excess of most other metals, because it is then reduced at a very much lower negative potential (the step is at about 0.2 v) than in the usual divalent form (for which E$\text{1}\text{2}$, is always greater than I v). The method is applied to the analysis of steels.After complexing by Trilon B small amounts of iron can similarly be determined in the presence of an excess of other metals. The method is applied to the determination of small amounts of iron in brasses and “pure” metals.     

ISolement du groupe des terres rares de l'apatite par l'acide di-(2-ethyhexyl)phosphorique (hdehp)

The liquid-liquid extraction of rare-earth elements (REE) by 0.75 M di-(2-ethylhexyl) phosphoric acid (HDEHP) in cyclohexane from perchloric acid (1–12M) has been investigated. At moderate perchloric acid molarities (1–6 M), the distribution coefficient, E, has an inverse third-power dependency upon the acid concentration in the aqueous phase. However, at higher perchloric acid concentrations, the slope of the resulting curve is about +18, which means a change in the extraction mechanism. In 12 M perchloric acid medium, REE are quantitatively and selectively extracted from apatite minerals, in the organic phase. In order to strip out all the lanthanides, back-extractions were carried out with 9 M hydrochloric acid solutions.     

Effect of medium pH on chemical selectivity of oxalic acid biosynthesis by <Emphasis Type="Italic">Aspergillus niger</Emphasis> W78C in submerged batch cultures with sucrose as a carbon source

The pH of the medium is the key environmental parameter of chemical selectivity of oxalic acid biosynthesis by Aspergillus niger. The activity of the enzyme oxaloacetate hydrolase, which is responsible for decomposition of oxaloacetate to oxalate and acetate inside the cell of the fungus, is highest at pH 6. In the present study, the influence of pH in the range of 3–7 on oxalic acid secretion by A. niger W78C from sucrose was investigated. The highest oxalic acid concentration, 64.3 g dm^?3, was reached in the medium with pH 6. The chemical selectivity of the process was 58.6% because of the presence of citric and gluconic acids in the cultivation broth in the amount of 15.3 and 30.2 g dm^?3, respectively. Both an increase and a decrease of medium pH caused a decrease of oxalic acid concentration. The obtained results confirm that pH 6 of the carbohydrate medium is appropriate for oxalic acid synthesis by A. niger, but the chemical selectivity of the process described in this paper was high in comparison to values reported previously in the literature.