Small-ring geminanes - New hypothetical molecules with inverted carbon atoms

Details of the molecular structures and properties of three novel hypotheti cal hydrocarbons that could possess inverted carbon atoms are revealed thro ugh post-Hartree-Fock ab initio calculations. Their molecular geometries we re optimized at the MP2 and DFT levels in conjunction with the 6-31G(d,p) a nd 6-311++G(d,p) basis sets. The calculated vibrational frequencies confirm that the predicted geometries represent minimum energy structures. The the oretically predicted chemical shifts reflect the unusual stereochemistry at the bridgehead atoms. All theoretical data indicate that for the studied m olecules three carbon atoms are located approximately in a plane with the c orresponding bridgehead atom.