Studies of nucleophilic attack on tris (pentafluorophenyl) phosphine and its oxides

The reaction of tris(pentafluorophenyl)phosphine [5] with the nucleophiles dimethyl formamide (DMF), hexamethylphosphoric triamide (HMPA), diethyl formamide (DEF), hexaethylphosphoric triamide (HEPA), hydrazine, N,N-dimethyl hydrazine (in presence and/or absence of KF), phenylhydrazine, ammonium hydroxide, formamide, aniline, sodium hydrogen sulfide, and hexaethylphosphorous triamide was investigated. The reaction of [5] with DMF and HMPA gave the same product, namely tris-[4-(N,N-dimethylamino)-2,3,5,6-tetrafluorophenyl]phosphine [12] but in higher yield in the case of HMPA. Compound (5] also reacted with DEF to give tris[4-(N,N-diethylamino)-2,3,5,6-tetrafluorophenyl] phosphine [14]. When [51 was treated with HEPA, it gave a mixture of bis(pentafluorophe~yl)-(N,N-diethylamino-tetrafluorophenyl)phosphine, pentafluorophenyl-bis-(N,N-diethylamino-tetrafluorophenyl)phosphine and tris (N,N-diethylamino-tetrafluorophenyl)phosphine. Treatment of [5] with aqueeus hydrazine solution in excess ethanol gave tris(4-hydrazo-2,3,4,6-tetrafluorophenyl)phosphine [1s1 in high yield while reaction with aqueous hydrazine led to C-P cleavage and production of tetrafluorophenyl hydrazine. With N,N-dimethyl hydrazine, [5] gave tris(4-N,N-dimethylhydrazine-2,3,5,6-tetrafluorophenyl) phosphine {20j. The latter could be obtained in higher yield and shorter reaction time, by the addition of KF. The reaction of compound {51 with phenylhydrazine in THF gave bis(pentafluorophe~yl)-4-S-phenylhydrazino- 2,3,5,6-tetrafluorophenyl phosphine [22] in low yield. Reaction of [5] with ammonium hydroxide in THF at high pressure in the presence of KF gave tris-~4-amino-2,3,5,6-tetrafluorophenyl)phosphine [25]. Similarly, formamide led to a mixture of (C6F4NHZ)3P, (C6F4NHZ)ZPC6FS, (C6F4NHZ)ZPC6F4NHCHO, and C6F4NHZP(C6Fs)(C6F4NHCHO). When [5] was treated with aniline, a mixture of mono-, di-, and tri-substituted products was obtained. Sodium hydrogen sulfide in ethylene glycol/ pyridine led to C-P cleavage and the isolation of pentafluorobenzene and tetrafluorothiophenol. Reaction of [5] and its oxide [35] with different alkoxides in the corresponding alcohols led mainly to C-P bond cleavage products, with the exception of one case where sodium methoxide was used in ether, and which led to tris-(4-methoxy-2,3,9,6-tetrafluorophenyl)phosphine [37]. On the basis of various spectroscopic data, it was concluded that the para position in compound [5] was generally the favoured site of attack.

Étude multicentrique sur les stratégies de ventilation mécanique employées chez les enfants avec un œdème pulmonaire lésionnel

Des études adultes sur l’œdème pulmonaire lésionnel et le Syndrome de Détresse Respiratoire Aiguë ont mené à l’établissement de recommandations sur les stratégies de ventilation mécanique à employer chez ces patients. Cependant, il n’est pas clair si les recommandations adultes sont également bénéfiques pour l’enfant. Objectif Décrire les stratégies de ventilation mécanique employées chez les enfants atteints d’un œdème pulmonaire lésionnel. Méthodes Étude épidémiologique transversale tenue dans 59 unités de Soins Intensifs Pédiatriques de 12 pays en Amérique du Nord et en Europe. Six jours d’étude ont eu lieu entre juin et novembre 2007. Les enfants atteints d’un œdème pulmonaire lésionnel étaient inclus et des données sur la sévérité de leur maladie, les paramètres de ventilation mécanique et les thérapies adjuvantes employées ont été recueillies. Résultats Des 3823 enfants dépistés, 414 (10.8%) avaient un œdème pulmonaire lésionnel et 165 (40%) ont été inclus dans l’étude (124 étaient sous ventilation mécanique conventionnelle, 27 sous ventilation à haute fréquence par oscillation et 14 sous ventilation non invasive). Dans le groupe sous ventilation conventionnelle, 43.5% étaient ventilés avec un mode contrôlé à pression, le volume courant moyen était de 8.3±3.3 ml/kg et l’utilisation de la PEP et FiO2 était hétérogène. Conclusions Cette étude démontre une hétérogénéité dans les stratégies de ventilation mécanique employées chez les enfants souffrant d’un œdème pulmonaire lésionnel. Celle-ci pourrait être en partie reliée à la robustesse des critères diagnostiques actuellement utilisés pour définir l’ALI/SDRA. Une évaluation rigoureuse de ces stratégies est nécessaire pour guider la standardisation des soins et optimiser l’issue de ces patients.

Facteurs liés à l’adoption du dossier médical électronique (DME): une étude de cas sur le processus d'implantation d’un DME dans un groupe de médecine de famille.

Dans l’espoir d'améliorer l'efficacité, l’efficience, la qualité et la sécurité des soins de santé, la plupart des pays investissent dans l’informatisation de leur système de santé. Malgré l’octroi de ressources substantielles, les projets d'implantation d’un Dossier médical électronique (DME) font parfois l’objet d’une résistance importante de la part des utilisateurs au moment de leur implantation sur le terrain. Pour expliquer l’adoption d’un DME par les professionnels de la santé, plusieurs modèles théoriques ont été développés et appliqués. Une diversité de facteurs agissant à différents niveaux (individuel, organisationnel et liés à la technologie elle-même) a ainsi été identifiée. L’objectif de cette recherche est d’approfondir les connaissances empiriques quant aux facteurs influençant l’utilisation du DME chez les professionnels de la santé. Le devis de recherche repose sur une étude de cas unique avec douze entrevues et une observation non participante réalisées un an suite au lancement du processus d’implantation d’un DME auprès d’un groupe de médecine famille (GMF) au sein du Centre de santé et de services sociaux du Sud-Ouest-Verdun (Montréal, Canada). Dans le cadre de cette étude, l’analyse a permis l’identification de facilitateurs et de barrières influençant l’adoption du DME. Les facilitateurs étaient l’utilité perçue, la décision du GMF d’implanter le DME, le support de la direction ainsi que la présence de champions et de superutilisateurs. Les barrières les plus importantes étaient l’impact négatif sur le travail clinique, la fragmentation de l’information dans le DME ainsi que les problèmes liés à l’infrastructure technique. Cette connaissance permettra d’alimenter des stratégies visant à mieux répondre aux défis suscités par l’implantation du dossier médical électronique.

Structure Absorption Spectra Correlation in a Series of 2,6-Dimethyl-4-arylpyrylium Salts

A combined experimental and theoretical study of the absorption spectra of a group of closely related pyrylium perchlorates 1-11 are presented. Minor changes in the position of the substituents lead to drastic changes in the absorption spectra in this series of compounds. We have attempted to explain the observed changes using the x,y-band notation developed by Balaban and co-workers. Absorption spectra of all compounds are compared with results from time-dependent density functional theory (TDDFT) and Zerner’s intermediate neglect of differential overlap (ZINDO/S) level calculations. Results of the calculations are in good agreement with experimental observations and an interesting correlation between Balaban’s notations and the MO transitions are obtained for simple derivatives. It is suggested that for more complex systems such as R- and â-naphthyl substituted systems, the empirical method is not appropriate.

Model Compound Studies on the Devulcanization of Natural Rubber Using 2, 3-Dimethyl-2-Butene

The mechanism of devulcanization of sulfur-vulcanized natural rubber with aromatic disulfides and aliphatic amines has been studied using 23-dimethyl-2-butene (C5H1,) as a low-molecular weight model compound. First C6H12 was vulcanized with a mixture of sulfur, zinc stearate and N-cyclohexyl-2-benzothiazylsulfenamide (CBS) as accelerator at 140 °C, resulting in a mixture of addition products (C(,H 1 i-S,-C5H 1 i ). The compounds were isolated and identified by High Performance Liquid Chromatography (HPLC) with respect to their various sulfur ranks. In it second stage, the vulcanized products were devulcanized using the agents mentioned above at 200 °C. The kinetics and chemistry of the breakdown of the sulfur-hridges were monitored. Both devulcanization agents decompose sulfidic vulcanization products with sulfur ranks equal or higher than 3 quite effectively and with comparable speed. Di phenyldisulfide as devulcanization agent gives rise to a high amount of mono- and disulfidic compounds formed during the devulcanization, hexadecylamine, as devulcanization agent, prevents these lower sulfur ranks from being formed.

A comparative study on aniline alkylation activity using methanol and dimethyl carbonate as the alkylating agents over Zn–Co–Fe ternary spinel systems

The catalyst compositions of the Zn1−xCOxFe2O4 (x= 0, 0.2, 0.5, 0.8 and 1.0) spiel series possessing ‘x’ values, x less than or equal to 0.5, are unique for selective N-monomethylation of aniline using methanol as the alkylating agent. Since dimethyl carbonate (DMC) is another potential non-toxic alkylating agent, alkylation of aniline was investigated over various Zn–Co ferrites using DMC as the alkylating agent. The merits and demerits of the two alkylating agents are compared. Catalytic activity followed a similar trend with respect to the composition of the ferrospinel systems. DMC is active at comparatively low temperature, where methanol shows only mild activity. However, on the selectivity basis, DMC as an alkylating agent could not compete with methanol, since the former gave appreciable amounts of N,N-dimethylaniline (NNDMA) even at low temperature where methanol gave nearly 99% N-methylaniline (NMA) selectivity. As in the case of methanol, DMC also did not give any C-alkylated products.

Selective Methyl Tert-Butyl Ether Synthesis over Metal Exchanged Pillared Clays

Iron and mixed iron aluminium pillared montmorillonites prepared by partial hydrolysis method was subjected to room temperature exchange with transition metals of the first series. The materials exhibit good structural as well as thermal stability. Exchanged metals were found to be present inside the porous network, in the environs of the pillars. Mixed pillaring resulted in the intercalation of Al 13 like polymers in which Al is partially substituted by Fe. The acidic structure was followed by temperature programmed desorption of ammonia and cumene cracking test reaction. Weak and medium sites overshadow the strong sites in all systems. However, exchange with metals increases the number of strong sites. The prepared materials are efficient catalysts for gas phase MTBE synthesis. The catalytic activity can be well correlated with the total amount of weak and medium acid sites.

Synthesis of dimethyl acetal of ketones: design of solid acid catalysts for one-pot acetalization reaction

The synthesis of dimethyl acetals of carbonyl compounds such as cyclohexanone, acetophenone, and benzophenone has successfully been carried out by the reaction between ketones and methanol using different solid acid catalysts. The strong influence of the textural properties of the catalysts such as acid amount and adsorption properties (surface area and pore volume) determine the catalytic activity. The molecular size of the reactants and products determine the acetalization ability of a particular ketone. The hydrophobicity of the various rare earth exchanged Mg–Y zeolites, K-10 montmorillonite clay, and cerium exchanged montmorillonite (which shows maximum activity) is more determinant than the number of active sites present on the catalyst. The optimum number of acidic sites as well as dehydrating ability of Ce3+-montmorillonite and K-10 montmorillonite clays and various rare earth exchanged Mg–Y zeolites seem to work well in shifting the equilibrium to the product side.