Isomeric distonic and H-bridged [C2H6O]+ radical cations

Ab initio molecular-orbital calculations (SD Cl/6-31G★★ confirm that the most stable [C2H6O]+ isomer is the distonic ion [CH2CH2OH2]+. Mass spectrometric measurements give ΔH0f, 298 = 732 ± 5 kJ mol−1. This ion interconverts with a yet-unidentified isomer, [CH2CH⋯H⋯OH2]+, a hydrogen-bridged water/ethene radical cation complex. The latter ion lies in a shallow well, 38 kJ mol−1 above [CH2CH2OH2]+ and 41 kJ mol−1 below the dissociation into [C2H4]+ and H2O. Above the interconversion barrier the isomers behave like ethene-ion/water-dipole complexes in which the dipole can move all around the ion. This behaviour may relate to the very small kinetic energy release in the dissociation.