A DFT HF STUDY OF THE POTENTIAL-ENERGY SURFACE OF PROTONATED ETHANE C2H7+/

Structures and energies of several isomers of the C2H7+ cation have be en calculated using the parametrized B3LYPHF/DFT method. The B3LYP/6-3 1G* geometries of the individual isomers are of at least the same qua lity as the MP2/6-31G* results. The zero-point-energy corrected relat ive stabilities of the individual C2H7+ isomers are in excellent agree ment with the much more costly MP4SDTQ/6-31G* MO calculations. A stru cture with a linear C-H-C skeleton and a CC distance of about 2.5 Angs trom was found to be a higher order saddle point on the PES resulting from curve crossing between the reactant and product channels CH3+ + C H4; this finding is of importance in interpreting the experimental res ults on the hydride ion transfer between CH3+ and CH4. The calculation s are also consistent with the earlier experimental results on the for mation of the products C2H5+ + H-2. (C) 1997 Elsevier Science B.V.