Force-field andab initio calculations of five-membered rings: II. Force constants and ab initio gradient calculations of the geometries of dioxoles and dithioles

Ab initio gradient calculations of the geometries of 1,3-dioxol-2-one, -thione, -onium, and the analogous 1,3-dithioles are reported. Together with force constants derived from GVFF calculations, these results give evidence of the changes in structure when substituting oxygen by sulfur. The electronic structure as well as the vibrational behavior are mainly determined by the electronic delocalization of the heteroatoms.