A THEORETICAL-STUDY ON THE ISOMERIZATION OF CYCLOPROPANE TO PROPENE WITH AB-INITIO AND DFT METHODS

The isomerization of cyclopropane to propene had been studied by ab in itio post-HF and DFT methods. Single-point energy calculations at UMP4 , UCCSD(T), UQCISD(T) and UBecke3LYP levels were carried out on the UM P2/6-31G* fully optimized structures. The reaction heat and activatio n energies for the whole isomerization reaction and the structural iso merization of the C-2-symmetry trimethylene intermediate were evaluate d. The correlation methods employed release an accuracy order of UBeck e3LYP > UQCISD(T) approximate to (UCCSD(T)> UMP4 > UMP2. UBecke3LYP is found to be the best method to reproduce the experimental results. Th e spin contamination problem can be solved by using projected MP energ ies. (C) 1997 Elsevier Science B.V.