POTENTIAL-ENERGY SURFACE OF THE C3H9- PROTONATED PROPANE( CATIONS )

The potential energy surface of the C3H9+ cations was calculated. At t he MP4(SDTQ)/6-311++G*/ /MP2(full)/6-31G** level of calculation, stru cture 4, representing the C-proponium cation, was the lowest in energy , but the van der Waals complex between the isopropyl cation plus hydr ogen lies only 0.3 kcal/mol above 4. The results of the calculations a re in good agreement with the experimental gas-phase energetic for the reactions involving the C3H9+ species. It was also calculated that th e interconversion of the 1-H-proponium cation to the C-proponium catio n involves no energy barrier and might be on a pathway explaining the formation of products ascribed to the direct C-C bond protonation in l iquid and solid superacids.