A MNDO study of planar thioacyl-substituted carbocations

Abstract

JACK LEON GINSBURG, RICHARD FRANCIS LANGLER, RAJ KUMAR RAHEIA, and LAURA PRECEDO. Can. J. Chem, 70, 11 1 (1992).Relative gas phase stabilities of pairs of planar regioisomeric thioacyl-substituted carbocations have been calculated using the MNDO method. These systems are stabilized by good T donors. The role of S T-electron population as a gauge of substituent effects is examined. Similar results were obtained using isodesmic reactions to gauge substituent effects. Results of this and earlier studies are consistent with the resonance saturation effect.Key words: semiempirical calculations, carbonium ions.JACK LEON GINSBURG, RICHARD FRANCIS LANGLER, RAJ KUMAR RAHEJA et LAURA PRECEDO. Can. J. Chem. 70, 11 1 (1992). Utilisant la mCthode MNDO, on a calcule les stabilitks relatives en phase gazeuse de paires de carbocations thioacyles substituks, rkgio-isomeres et plans. Ces systkmes sont stabilisks par de bons donneurs d'klectrons T. On a kvaluk le r61e de la population S d'klectrons T comme mesure des effets de substituants. On a obtenu des rksultats semblables lorsqu'on a utilisk des rkactions isodesmiques comme mesure des effets de substituants. Ces rksultats et ceux obtenus au cours d'ktudes antCrieures sont en accord avec un effet de saturation par rksonance.