Etude theorique de la cycloaddition de l'ozone sur l'ethylene

A theoretical study of the cycloaddition of ozone on ethylene has been carried out by the LCAO-SCF-MO method. The potential energy hypersurface for the reaction has been investigated and the electronic and energetic properties of the transition state have been determined.     

Etude theorique de la cycloaddition de la nitrone sur l'ethylene

A theoretical study of the concerted 1,3-dipolar cycloaddition of nitrone on ethylene has been carried out by the LCAO-SCF-MO method. The potential energy hypersurface for the reaction has been investigated and the characteristics of the transition state have been determined.     

Etude calorimetrique et analytique de l'adsorption du cyanogene sur la silice

The adsoprtion of C₂N₂ on well outgassed specimens of SiO₂ at temperatures from 35 to 913°C has been studied by heat flow calorimetry, volumetry, and mass spectrometry.Small amounts of cyanogen are adsorbed at low temperature: reversibly by hydrogen bonding with the silanol groups, and irreversibly on strained siloxane bridges or Lewis acid sites. Above 200°C cyanogen reacts, with silanol groups, leading to the formation of HCN (partly reversibly adsorbed on non-reacted silanol groups) and silyl isocyanate:

. The process is complete at 418°C and the measured enthalpy for the reaction

is ΔH = ?12.2 ± 0.3 kcal mole^?.Above 500°C, HCN and C₂N₂ react with ordinary siloxane bridges. At higher temperature, the pyrolysis of

produces CO₂ with CO and N₂ (in smaller quantities), showing that a large proportion of N-atoms are bonded on the surface.     

Etude de la metallation de l'oxyde de diferrocenyl phenyl phosphine

The reaction of n-BuLi with phenyldiferrocenylphosphine oxide yields a mixture of two isomeric dianions. This mixture reacts with Me₃SiCl, Br₂, CO₂, PhCHO and PhCHNPh to give bifunctional products. With CoCl₂, Me₂SiCl₂, Ph₂SiCl₂, Bu₂SnCl₂ and PhCOOEt, the same mixture gives cyclic products. In almost every case each of these compounds is a mixture of two isomers corresponding to the original compound. The characteristic patterns of the PMR spectra are in full agreement with the structures proposed for the isomeric dianions.     

Etude de l'action des alkylmagnesiens primaires et arylmagnesiens sur les anhydrides tricycliques pontes

The reaction of primary alkyl and aromatic Grignard reagents with bridged tricyclic di-carboxylic anhydrides gives the corresponding dialkylated tricyclic lactones via di-addition process. The lactones were transformed by retro-Diels-Alder reactions into 4,4-dialkylated butenolides.     

Influence de la longueur d'onde sur la photoisomerisation de derives de l'hexatriene-1,3,5

Kinetic studies of photoisomerization of 1-phenyl 6-methyl-cyclohexa-1,3-diene, and of the four isomeric 5-phenylhepta-1,3,5-trienes, have been performed at 313, 254, 228 and 214 nm. Photoreactions of these compounds are dependent on the wavelength of irradiation. Photolysis at short wavelength of Z,E-5-phenylhepta-1, 3,5-triene initiates a new reaction, sigmatropic [1,5] hydrogen migration, forming an ene-allenic compound. Thermal reactivity data for polyenic compounds supports the assigned structures.     

Etude de l'aromaticite par la theorie de hückel

Dewar theory and Breslow theory of aromaticity in contrast to Kruszewski-Krygowski theory, do not regard aromaticity as a chemical property, resulting in numerous contradictions between experimental behaviour of hydrocarbons and theoretical expectations are observed. Two new indexes can be introduced into the Kruszewski-Krygowski's theory,² one concerned with hydrocarbon stability, the other with its aromatic character.     

Etude de l'equilibre entre l'oxyde de nickel et l'oxygene. Essai d'interpretation des lois de variation de la conductivite electrique en fonction de la temperature

In a previous paper we have shown that at 740°C and under an oxygen pressure less than 1,3 torr the electrical conductance G of a NiO powder reaches rapidly an apparently stabilized signal G_i which sharply decreases after a sufficiently long time to a G₀ value independent of P_O2.From this observation we have studied the influence of the temperature successively on the electrical conductance G_i and G₀. The Arrhenius law is only verified for the G₀ = f(T) curve. G₀ appears as the representative value of the gas-solid equilibrium.     

Influence de la conformation des polyions sur la fixation de colorants—III. Etude de la fixation de l'auramine o sur des polyacides synthetiques par equilibres de dialyse

The binding of auramine O (AuO), a cationic dye which does not dimerize, to poly(methacrylic acid) (PMA) and poly(acrylic acid) (PAA) has been measured by dialysis experiments. The effects of ionization, ionic strength and polymer to dye ratio (P/D) have been systematically investigated. At low ionization and P/D = 100, the bound fraction (q) of AuO is distinctly higher with PMA than with PAA at all ionic strength; this difference can be attributed to non-electrostatic interactions. Increase of ionic strength leads to displacement of the bound dye; on the other hand, high P/D ratio favours binding. We were able to describe the binding isotherms by an ion-exchange process at constant ionization and ionic strength. Water-methanol mixtures, known to destroy the coiled conformations of PMA, lead to a decrease in q; the same is observed in unionized acidic PMA solutions where ionic interactions are suppressed. These results indicate a strong binding due to the insertion of the dye into the polyion compact core and also a weak electrostatic one; they agree with the observations of spectrofluorescence; it must be emphasized that the bound fraction of dye is not, in itself, a significant parameter of conformational states.     

Remarques sur la cinétique de l'oxydation à l'air du monoxyde de titane

Thermogravimetric results on the oxidation of TiO by air obtained by one of the authors (M. J. Blais) and untimely exploited by Garnaud¹ are placed in bibliographical outline, described more in detail and carefully rediscussed.     

Influence des solvants sur la copolymérisation de l'acrylamide avec l'acrylonitrile

The copolymerization of acrylamide with acrylonitrile was investigated in various solvents, which can be put into three groups according to their influence on molecular associations; (1) solvents autoassociated by hydrogen- bonds (acetic acid, methanol, water, dimethylformamide); (2) polar solvents which can associate with the NH group of acrylamide (acetonitrile, dioxane, acetone); (3) inert solvents (toluene, benzene, hexane). The reaction kinetics and the compositions of the copolymers are different for each group of solvents. The composition of copolymers formed in solvents of group 1 vary widely, depend- ing on the solvent. Copolymers formed in all solvents of group 2 have the same composition which is that of copolymers formed in bulk. The amount of acrylamide is highest in copolymers formed in inert solvents of group 3. Such parameters as the degree of conversion, the reaction temperature, the mode of initiation and the extent of dilution only slightly affect the composition of copolymers. Homopolymerizations of acrylamide and acrylonitrile were investigated in all solvent used.The results suggest that the effects of solvents on the copolymerization of acrylamide with acrylonitrile are consequences of the various modes of molecular association of acrylamide. The solvents affect the equilibrium between auto- association of acrylamide and its association with solvent and thereby affect the reactivity of the monomer.     

Influence de la temperature sur les manifestations de l' “effet de matrice” dans la polymerisation de l'acide acrylique en solution

This study is concerned with the influence of temperature on the kinetics of the polymerization of acrylic acid dissolved in dioxane or toluene and on the type of molecular association complexes present in these solutions. In dioxane solutions, an increase in temperature destroys the oligomeric auto-associations of acrylic acid and gives rise to monomer-solvent associations. Simultaneously, the consequences of the “matrix effect” (auto-acceleration and stéréospecificity) become less pronounced. In contrast, in toluene solutions, an increase in temperature converts the cyclodimeric auto-associations of the monomer into linear oligomers and the consequences of the matrix effect appear (or become more pronounced). The Arrhenius plots exhibit anomalies which conform with the above interpretation. The results obtained in dioxane and in toluene solutions are similar to earlier findings in methanol and n-hexane solutions respectively. This makes it possible to generalize the conclusions reached here to acrylic acid solutions in other solvents which may or may not associate with the monomer.     

Sur la reactivite des organomagnesiens derivant de l'addition d'organomagnesiens allyliques sur l'isoprene

Contrary to a recent report, it is shown that allylic Grignard reagents prepared by treating allylic Grignard reagents with isoprene and a catalytic amount of Cp₂TiCl₂ react normally with carbon dioxide and carbonyl compounds: a complete allylic rearrangement is observed.     

Influence des solvants sur les associations moleculaires et sur la cinetique de polymerisation de l'acrylonitrile. Precisions supplementaires sur l'“effet de matrice”

The polymerization of acrylonitrile is auto-accelerating in bulk and in solvents which do not dissolve the polymer. The “auto-acceleration indexes” remain almost constant in these systems. Trichloracetic acid, a very polar solvent, leads however to linear conversion curves. An earlier assumption is confirmed according to which auto-acceleration is not caused by non-stationary conditions but by an oriented association complex between the monomer and the polymer arising at the beginning of the reaction (“matrix effect”). DMF, a solvent for polyacrylonitrile, seems to produce a similar effect. The disappearance of auto-acceleration in DMF solutions was explained until now by the disappearance of the perturbation of the reaction connected with polymer precipitation (“occlusion effect”). Linear conversion curves were obtained, however, in 60% DMF solutions in which the polymer still precipitates. A detailed study of post-polymerization confirms the above interpretation. It is shown that auto-acceleration remains unaltered in the presence of solvents which swell polyacrylonitrile, such as acetonitrile or small amounts of DMF, whereas post-polymerization (caused by occluded chains) is strongly reduced. Moreover, a marked post-polymerization is observed in the presence of trichloracetic acid, demonstrating the presence of long-living chains in a system which gives rise to linear conversion curves. The association of acrylonitrile with numerous solvents is investigated; it is shown by swelling measurements that polyacrylonitrile associates with its monomer.     

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.