Controle de la qualite des materiaux colles a partir du mode vertical

The paper presents measurements by transmission of an ultrasonic wave on glued sheet immersed in water. The experiments was performed by varying the incidence angle. The study has been undertaken on structures consisting of two identical plates either of aluminium or of steel glued by an epoxy resin. The obtained results reveal the existence of a vertical mode which allows to control the quality of the assembly.     

Sur le comportement photochimique des 19-nor Δ-steroides

The condensation of 3:5-dichloro-2hydroxy acetophenone with various aldehydes afforded chalcones, which were converted into the corresponding 6:8-dichloroflavanones by the action of dilute ethanolic hydrochloric acid. The oxidation of chalcones by means of selenium dioxide and by alkaline hydrogen peroxides gave 6:8-dichloro-flavones and -flavonols respectively. Incidentally, some chalcones from 3:5-dichloro-2-methoxyacetophenone were also prepared.     

Diazoalcanephosphonates. Etude par RMN du proton de la configuration de Δ1-pyrazolines dérivées du norbornadiène

The NMR spectra of eleven pyrazolines 1 to 11 derived from norbornadiene are interpreted and discussed. The configurations are deduced from the vicinal P?C?C?H₁₀ coupling: this is ～20 Hz in the anti derivatives and ～6·0 Hz in their syn epimers. The long-range P,H₉ coupling is stereospecific, being maximum for a syn configuration.     

Spectres de Masse de la Methyl-2 Thiazolidinethione-2 et de la Dimethyl-2,4 Δ2-Thiazoline

The mass spectra of the title compounds point to rupture of S? C-2 and N? C-4 bonds as being the dominant reaction under electron impact. 13C labelling of a selected position of the ring allows some fragmentation pathways to be confirmed.     

Polarisation nucleaire induite chimiquement: etude comparative de la decomposition thermique et photochimique de peroxydes d'acyle benzoyle

A comparative CIDNP study of the thermal and photochemical decomposition of acyl benzoyl peroxides PhCO₂O₂CR (R = methyl and isobutyl) has provided an explanation of the effect of the mode of initiation on the course of the decomposition of this class of peroxides and on the product distribution. The observed variations result from an important decrease (from 10^?8 sec to less than 10^?10 sec) in the lifetime of the benzoyloxy radical on changing from thermal to photochemical initiation.     

Influence de l'Insaturation Δ20(22) sur la Fragmentation du Cycle D des Stéroides

The mass spectra of two series of Δ20(22) unsaturated steroids have been studied. The analysis of the D-ring fragmentation shows that C-15? C-16 bond rupture is characteristic of the presence of this unsaturated sidechain.     

Contribution a l'etude de la decomposition thermique du carbonate de cadmium

The thermal decomposition of CdCO₃ has been studied by DTA on samples of different origins. A classical experimental device enables work at different pressures up to 12 bar for any gas used. Evaluation of the data measured by the author and their comparison with those given by others show that the carbonates obtained by the chemical method are different from those prepared by hydrothermal crystallization. As the latter exhibit higher thermal stability, they may permit a further, real thermodynamic study on the decomposition of cadmium carbonate.     

Etude du comportement photochimique de complexes {PtCl2(oléfine)(amine)}, influence de la nature de l'olefine et de la configuration du complexe

Irradiation of complexes {PtCl₂(olefine)(amine)} leads to the departure of the olefinic ligand forming a dimeric compound {PtCl₂(amine)}₂ which has a trans configuration. The same behaviour is observed at different irradiation wavelengths, with variation of the nature of the coordinated olefin and with a cis or trans configuration of the starting compound. Experimental results show that the primary photochemical reaction pathway arises probably via a (d → π^★ C₂H₄) charge transfer existed state. A simultaneous cis → trans photoisomerization is observed in the case of the cis complexes.     

Etude thermodynamique de la decomposition thermique des hydrates du chlorure de magnesium

The thermodynamic study of the different compounds of the system MgCl₂, H₂O, HCl allows to draw the stability diagram of the 8 solid phases into a three-dimensional space (temperature, total pressure and ratio of HCl and H₂O partial pressures). The evolution of the composition of solid and gaseous phases during an isobaric heating is described. The conclusions of this study are in good agreement with the experimental results obtained in laboratory and with the industrial requirements set for the different steps of the dehydration of MgCl₂.     

Etude cinétique de l'ouverture du cycle Δ2 imidazoline par hydrolyse basique

The kinetics of base hydrolysis of two Δ₂ imidazolines were followed by uv spectroscopy in sodium hydroxide and in carbonate buffers. In the most basic medium the rate of hydrolysis is independant of pH. This is explained if the rate determining step is attack of hydroxide ion on the protonated form of the substrate. In less basic medium there is a change in the slow step, the breaking of the intermediate becomes rate determining.     

Etude cinetique non isotherme de la decomposition thermique du complexe dipyridinique de bromure de cadmium

Résumé Les paramètres cinétiques de la décomposition du complexe CdPy₂Br₂ ont été déterminés à l'aide de plusieurs méthodes nonisothermes à l'aide des données fournies par la thermogravimétrie et l'ATD. Les valeurs obtenues concordent de faÇon satisfaisante.

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Six nonisothermal thermogravimetric and DTA methods have been applied for determining the kinetic parameters of the decomposition of CdPy₂Br₂. The values obtained are in satisfactory agreement.

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Zusammenfassung Die kinetischen Parameter der Zersetzung des Komplexes CdPy₂Br₂ wurden durch verschiedene nicht-isotherme Methoden, durch Thermogravimetrie und Differentialthermoanalyse bestimmt. Die Resultate stimmten gut überein.

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6 CdPy₂Br₂. .

     

Problemes de stereoselectivite en serie du benchrotene: cyclisation des acides α- et β-alcoyl β-phenyl propioniques. Influence de l'encombrement sterique sur la stereochimie de la reaction

The cyclisation in polyphosphoric acid of α-alkyl-β-phenylpropionic acids gave rise to exo and endo diastereoisomers of indanone-Cr(CO)₃. In both cases selectivity appears to be under steric control in spite of fundamental differences. The use of optically active substrates to ascertain the endo and exo configurations is described. A method based on optical isomery has allowed the determination of the kinetic product in a thermodynamically controlled reaction     

Polarisation nucleaire induite chimiquement: etude du mecanisme de la decomposition thermique de peracides dans l'hexachloroacetone

The study of peracids thermal decomposition in hexachloroacetone shows that the pair which originates CIDNP signals on the obtained products is not $\text{R}{}^{\mathrm{..}}\text{OH}$ but $\text{R}{}^{\mathrm{..}}\text{CCl}{}_3$.