Etude par analyse thermique de quelques vegetaux mediterraneens

Thermal analysis can be used for the study of the behaviour of plants during heating, and most particularly in the risk prevention of forest fire.Simultaneous thermal analysis (DTA-TG) of some mediterranean vegetals (needles of Pinus halepensis, leaves of Quercus coccifera; leaves of Rosmarinus officinalis; prickles, flowers and branchs of Ulex parviflorus; leaves and branchs of Acacia dealbata; leaves of Cistus albidus) shows the presence of several exothermic peaks. The first one, about 300°C, is responsible for a brutal ignition of the evolved gas. We compare the different samples by using the DTA and DTG peak temperatures and the weight loss by volatilization at 300°C.

     

Etude de la racemisation induite par la dmap dans les reactions de couplage peptidique

The scope and limitation for the use of 4-dimethylamino pyridine (DMAP) as additive to carbodiimides in peptide synthesis are studied and compared with the results obtained with H-hydroxybenzotriazole (HOBt). The activation of N-acylated aminoacids by the means of DMAP leads to a complete racemization. On the other hand, for the aminoacids protected under their urethans derivatives, DMAP gives better yields than HOBt with racemization extent generally equal to or slightly higer to that observed with HOBt.     

Etude par analyse thermique des sels de calcium de quelques acides alcanesulfoniques

Calcium salts of some alkanesulphonic acids have been prepared. Most of them are new. Their dehydration and the decomposition of anhydrous salts have been studied by thermogravimetric analysis (TG) and by thermal differential analysis (DTA) under ordinary pressure. In an inert atmosphere the sulphides formed indicate that carbon-sulphur and oxygen-sulphur bonds have been broken. The mechanism of decomposition of the calcium alkanesulphonates seems to be more complicated than that of the corresponding carboxylates.     

Etude comparative par analyses thermique et chimique de quelques vegetaux mediterraneens

Thermal analysis can be used for the behaviour of plants during heating and most particularly in the risk prevention of forest fire. Cellulose, holocellulose and lignin are the most important compounds determinated by analytical procedures in six mediterranean vegetals: Acacia dealbata, Pinus halepinsis, Quercus coccifera, Rosmarinus officinalis, Thymus vulgaris, Ulex parviflorus. TG-DTA is applied to the powders obtained after drying (110°C), pounding and sifting. The rate of pyrolysis about 300°C allows a semi-quantitative estimate of the cellulose present in the vegetal and its flammability.

Nous tenons à remercier, pour leur collaboration technique, mesdames J. Campocasso, A. Crestin et M. F. Vergnes.     

Etude par RMN d'une inversion de cycle de quelques benzodiazépinones

The NMR spectra of five benzodiazepinones are determined over a range of temperature. They indicate that the seven ring has a twist-boat shape, which inverts more or less rapidly according to the nature of substituents. The activation parameters and the rates of inversion are determined and the substituent effects are discussed.     

Determination quantitative des impuretes des graphites nucleaires par les methodes de radioactivation analyse systematique

Impurities contained in nuclear graphites have been determined so far individually. A method of systematic analysis is described which permits to determine about twenty impurities in one sample, such as the following elements: Ag, Se, Hg, Sb, Cu, Fe, Ga, Co, Cd, Zn, In, Zr, Cr, Sc, Ba, Ca, Na, K, Rb, and Cs. Brief mention is made of methods used for the determination of all rare earth metals, Si, S and P, as well as the elements which can be determined without chemical separation, such as Cl, Mn, V.

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Determination quantitative des impuretes des graphites nucleaires par les methodes de radioactivation analyse systematique

     

Etude de la conductivite anionique dans quelques fluorures amorphes obtenus par hypertrempe

Fluoride ion conductivity has been investigated in amorphous materials obtained in the BaF₂-ZnF₂, PbF₂-ZnF₂ and BaF₂-MnF₂ systems using both NMR and complex impedance techniques. The activation energies appear to be about 0.53 eV with a good agreement between both methods. Ionic conductivities have been found to be larger than 10^-5ω^-1cm^-1 at 180°C, values which are among the best ones so far obtained for fluorine conducting glasses.     

Etude de quelques polystyrenes ignifuges

The objective of this work is to study a few samples of fire-proof polystyrene. Determination of density, the search for fire retardants and halogen assessment as well as thermal behaviour, are studied by DTA and TG. All make it possible to distinguish among the samples and to classify them according to the chloride and bromide, fire-proofing agents content.

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Zusammenfassung Gegenstand dieser Arbeit war die Untersuchung von feuerfesten Polystyrolen.Sowohl die Bestimmung der Dichte, die Untersuchung auf Flammenhemmer und Halogene als auch die Untersuchung des thermischen Verhaltens mittels DTA und TG ermöglichen eine Differenzierung der Proben und eine Klassifizierung nach Gehalt an Chlorid, Bromid und Flammenhemmer.

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Ce travail a été réalisé avec l'aide de A. ASTIC et V. BURG stagiaires de la MST des Méthodes et Valorisation de la Chimie Fine (MARSEILLE).Nous remercions tout particulièrement l'ANVAR qui a contribué à cette étude grâce à l'octroi de deux APIES; Madame E. BONNET du Departement Additifs plastiques et Produits industriels de CECA, filiale d'ATOCHEM (anciennement M & T CHIMIE) qui a fourni les échantillons et Monsieur M. BERNARD du CRITT — CHIMIE Matières Plastiques (MARSEILLE).     

Etude par spectrographie d'absorption infra-rouge de quelques complexes aquoamminés du nickel

Résumé Un essai d'interprétation des spectres d'absorption infra-rouge, entre 200 et 4000 cm^–1, des sels de nickeloaquopentammine et de nickelo-diaquotétrammine a permis d'obtenir un aperçu sur la structure de quelques autres complexes du nickel. En particulier, l'étude du déplacement de la bande de vibration de déformation symétrique de l'ammoniac avec l'espèce chimique a servi à déterminer la pureté de sels de nickelohexammine d'après leurs spectres.

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Summary An interpretative study of the infra red absorption spectra, between 200 and 4000 cm^–1, of the salts of nickeloaquapentammine and of nickelo-diaquatetrammine has given an insight into the structure of several other nickel complexes. In particular, the study of the displacement of the vibration band of symmetric deformation of ammonia with the chemical species has served to determine the purity of salts of nickelohexammine from their spectra.

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Zusammenfassung Der Versuch einer Interpretation der Infrarotabsorptionsspektren von Aquopentamminnickelaten und Diaquotetramminnickelaten zwischen 200 und 4000 cm^–1 gab einen Überblick über die Struktur einiger anderer Nickel-komplexe. Insbesondere diente die Untersuchung der Verschiebung der symmetrischen Schwingungsbande zur Reinheitsbestimmung von Hexammin-nickelaten auf Grund ihrer Spektren.

     

Analyse de traces par utilisation simultanee d'un abraseur ionique et des techniques de reactions nucleaires

Résumé On associe un faisceau d'ions de basse énergie (abraseur ionique) à un ensemble de microanalyse par observation directe des réactions nucléaires. Le système permet de tracer des profils de concentration par abrasion-comptage. Les résultats obtenus concernent: (a) la mesure des profils d'impureté (bore, phosphore) dans le silicium et le ZnTe. (b) l'étude de la diffusion de l'oxygène sous un flux de neutrons dans le niobium et le nickel.     

Etude de steroides fluores par spectrometrie de masse—III: Spectres de masse de quelques cetones fluorees

A series of 24 fluorinated steroidal ketones was studied by mass spectrometry. The different locations of the keto group or fluorine atom, permitted of fragmentation patterns to be derived.     

Dosage des impuretes O,N. C dans les materiaux purs par la methode d'activation dans les neutrons rapides et les quanta γ

Résumé Nous décrivons les méthodes de dosage de O, N et C par activation dans les neutrons et les γ. Notre attention principale a été consacrée à écarter l'influence des contaminations de surface et à contr?ler l'efficacité de la séparation des isotopes¹⁵O,¹³N,¹¹C.     

Etude par RMN du mecanisme des reactions de transcomplexation entre les sels de chloroiminium (reactifs de vilsmeier) et les amides ou thioamides. Appl

Previous studies have established the existence of an acid-base equilibrium between the Vilsmeier complex (Me₂NCHCl)⁺ B^? and dimethylformamide. It is shown that the behaviour of chloroiminium salts as Lewis acids towards amides or thioamides is a general phenomenon. When the acids and bases are differently substituted, the reaction may have synthetic applications.     

Analyse du phosphore dans le silicium par reactions nucleaires

The determination of phosphorus is presented using the³¹P(p, α)²⁸Si reaction. The principle of the method and the instrumentation are discussed as well as the precision, sensitivity and the influence of the target thickness. The method is especially suitable for the investigation of diffusion phenomena. The concentration profiles are shown in silicon samples for various times of pretreatment. The interpretation of the profiles is given.      

Etude du dosage de 30 elements par activation dans les protons de 11 MeV

We have irradiated 30 elements with 11 MeV protons and we present here: (1) The specific activities for the main radioisotopes produced by (p, n) or (p, α) reactions (on main γ rays except the 511 keV). (2) The main γ energies of these radioisotopes (at ±0.3 keV) when they have not been accurately measured previously. (3) The limits of detection or the lowest amounts measured in samples of Al, Ag or Co. From these preliminary results it can be deduced that 11 MeV protons offer new possibilities in the field of activation analysis.      

Analyse par observation directe de reactions nucleaires de l'oxygene et du carbone au voisinage de la surface d'echantillons de bore

Ion-beam surface analysis of light elements such as oxygen and carbon in light matrices (boron in our case) is mainly subject to matrix interferences. Using a telescope detection system we show that (d, p) reaction for carbon and proton backscattering for oxygen are able to lead to concentration profiles on the first microns of bulk boron samples. Data processing is described and analytical results are shown, making evidence of the purification obtained using electronic bombardment furnace. Comparing with other phhsical methods of analysis, limitation and improvements of this procedure are discussed.      

Etude des reactions des diazoderives avec les cycloimmonium ylures-I : Action des sels de diazonium sur quelques pyridinium - ylures

The synthesis of cycloimmonium salts of the type $\text{7}$, $\text{8}$ and the corresponding cycloimmonium ylides $\text{9}$, $\text{10}$ are reported. In the reaction with diazonium salts $\text{11}$, $\text{12}$ the pyridinium monosubstituted carbanion ylides $\text{9}$, $\text{10}$ give the pyridinium disubstituted carbanion ylides $\text{17}$ – $\text{20}$. These are new types of isolable stable ylides. The synthesis involves the formation “in situ” of ylides $\text{9}$, $\text{10}$ which are bonded by their nucleophile ylide carbon atom to the nitrogen atom in diazonium salts. The intermediat formation of cycloimmonium salts $\text{13}$ – $\text{16}$ must be accepted. The structures of all compounds presented in this paper have been established by using elementary analysis, IR and ¹H-RMN spectra.