Vous avez des questions?Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Functional group polysulphones by bromination-metalation Guiver, Michael D.; Kutowy, O.; ApSimon, John W. https://publications-cnrc.canada.ca/fra/droits L'accès à ce site Web et l'utilisation de son contenu sont assujettis aux conditions présentées dans le siteA variety of functional groups can be substituted on aromatic polysulphones by a process of bromination followed by metalation. Both Udel polysulphone and Radel polyphenylsulphone were brominated at room temperature using bromine without a catalyst. Repeat units containing two bromine atoms at the electrophilic site in the bisphenol portion were obtained when excess reagent was used. These polymers readily undergo metal-halogen exchange with n-butyllithium. The resulting polyanionic lithiated polysulphones are reactive to a variety of electrophiles and give polymers containing functional groups such as carboxyl and hydroxyl. These polymers are useful as membrane materials.

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. Can. J. Chem. 55,2813Chem. 55, (1977.Substituent parameters were derived for the semiempirical determination of 13C chemical shifts in saturated hydrocarbons, alcohols, amines, ketones, and olefins. The olefin parameters are valid for six-membered rings and the remaining parameters for six-membered rings in chair conformations. We have shown that P-carbon substituent double bond subslituent effects suggested that effects on 13C resonances are related to the the y-group has not introduced a new shielding number of hydrogen-carbon (HC) and carbonmechanism which fortuitously cancels the HC carbon (CC) gauche interactions (1). Similarly, shift increment, but rather that it has eliminated P-heterosubstituent effects depend on the num-the HC shift contribution (3).' In other words, ber of hydrogen-heterosubstiluent (HX) and the observed gauche y-effect is not associated carbon-heterosubstiluent (CX) gauche inter-with the y-group but with the elimination of the actions (2). If a gauche y-substituent is added to H an HC configuration, one observes a displacement which is equal in size, but opposite in sign, to the HC shift increment. An investigation of For personal use only.

1 (1990).The isolation and characterization of a novel triterpene glycoside from the sea cucumber Cucumariaji-ondosa, collected from the Gulf of St. Lawrence, are described. Physico-chemical data obtained on the underivatized saponin are presented in support of structure 1 for frondoside A. The structure is characterized by the presence of a branched oligosaccharidic chain composed of five units. The holostane-type aglycone features an endocyclic double bond at position C-7,8 and a P-acetoxy group at C-16. On dCcrit l'isolation et 1'Clucidation structurale d'un nouveau triterpkne-glycoside, obtenu de l'holothurie Cucumaria ji-ondosa provenant du golfe du St-Laurent. En se basant sur les donnCes physico-chimiques du produit intact, on propose la structure 1 pour le frondoside A. Le composC est caractCrisC par la presence d'une chaine oligosaccharidique branchke, de cinq unites. L'aglycone de type holostane posskde une insaturation en position C-7,8 et un groupement acCtoxy-P en C-16.