Jean Pierre Fayet

Molecular modelling of the isothiazolo[5,4-b]pyridin-3(2H)-one derivatives

Abstract The performance of several semiempirical (MNDO, AM1, PM3, and SAM1) and ab initio (HF and MP2/6-31G ∗ ) methods for describing the structural and electronic features of a series of isothiazolopyridines, some of them bearing a hypervalent sulphur, is compared. Most of semiempirical methods calculate reasonable molecular structures, as compared with X-Ray structures, even in the case of S -oxides and S , S -dioxides. However, dipole moments are barely reproduced by these methods, even in the case of SAM1, which includes d orbitals. Hartree-Fock ab initio calculations do not lead to good dipole moment values in the case of S , S -dioxides. The agreement with experimental values is much better in the case of second order Moller-Plesset calculations, but this seems to be due to the systematic differences found between HF and MP2 values.

Etude structurale de trialkylalcoxy-ou aryloxygermanes et d'oxydes de trialkylgermyle : I. Determination des polarisations atomiques de tetraalkylgermanes et d'oxydes de trialkylgermyle

Abstract The atomic polarizations of tetraalkylgermanes and oxides have been determined. The total molecular polarizations are measured by dipolarimetry at various temperatures; the electronic polarizations have been obtained from dispersion of the refractive index.

Etude structurale de trialkylalcoxy- ou aryloxygermanes et d'oxydes de trialkylgermyle : II. Influence du solvant sur les polarisations atomiques des oxydes de trialkylgermyle: Determination par dipolemetrie des angles GeOC et GeOGe

Abstract The dipole moments of trialkylalkoxygermanes, phenoxy- and p -chlorophenoxygermanes of the type R 3 GeOR′ with R = Me, Et, Pt, Bu, and R′ = Me, t-Bu, Ph, p -ClPh, and also the trialkylgermanyl oxide compounds of the type R 3 GeOGeR 3 with R = Me, Et, Pr, have been determined in both cyclohexane and benzene. As a result of studies at various temperatures (25,45,65°C) we were able to measure the atomic polarization. These data indicate an important variation with the nature of the solvent. It is observed that oxygen valence angles change with the nature of the substituents and that the moments of the R 3 GeO groups are modified only slightly irrespective of the nature of R or the solvent.