Accurate theoretical structures of radical cations containing unusually long bonds: The structures of CH3CH2OH center dot+, CH3CHO+H2 and CH2CH2O+H2

A detailed investigation of the structures of CH3CH2OH.+ and its alpha- and beta-distonic isomers, CH3CHOH2 and CH2CH2OH2, has been carried out using a variety of theoretical procedures. The methods employed include Hartree-Fock theory and a range of correlated procedures including second-order Moller-Plesset (MP2) theory, quadratic configuration interaction (QCISD, QCISD(T)0, and coupled-cluster theory (CCSD, CCSD(T)), as well as the density functional theory procedures B3-LYP and B3-P86. It is found that the use of a reliable electron correlation procedure, as well as a reasonable sized basis set, are important in accurately determining the structure of such ions. At the highest level of theory employed in this study (CCSD(T)/6-311G(d,p)), CH3CH2OH.+ is predicted to possess an unusually long C-C bond (1.745-angstrom) while CH2CH2OH2 is predicted to contain an unusually long C-O bond (1.614-angstrom).