13C-and 170-relaxation times measured in cyclic ethers, cyclic ketones, and lactones allowed the determination of the quadrupolar interaction at the 0-site. Values obtained for six-membered rings can be used as standard values for ethers k = 13 MHz), ketones (il= 10.5 MHz), and esters c;C= 11.5 MHz for dicoordinated and 9.5 MHz for monocoordinated 0-atom). Even within a series, no correlation is found between the 170-chemical shift and the value of quadrupolar interaction. Introduction. -Les dkplacements chimiques de 1 7 0 sont connus pour de nombreuses series de produits homologues [I]. Des regles empiriques reliant les dkplacements entre eux ou A d'autres proprietts moleculaires ont ainsi ete etablies [ 2 ] . En dkpit de progres rkcents, nous ne disposons que de peu d'information [3] concernant les constantes de couplage quadrupolaire (CCQ.), interessantes a determiner pour elles-mCmes, et qui, de plus, interviennent directement en RMN. de 1 7 0 en conditionnant la largeur des raies. Dans ce travail nous nous proposons d'une part de determiner les CCQ. de l'atome d'oxygene pour des series de composts cycliques presentant diverses fonctionnalitks et, d'autre part, de discuter la relation entre l'interaction quadrupolaire et le deplacement chimique. y 4 5 1 1 3 bX, 4 2 3 4 X = O,CH:, Y = 0 , C H 3 ~ I)Auteur a qui la correspondance doit &tre adressCe. Adresse actuelle:
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