J. K. Terlouw

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

Abstract 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.

The isomeric ions produced by the gas phase protonation of HNCO and HCNO

Abstract Ab initio molecular orbital theory calculations combined with mass spectrometric experiments show that the gas phase protonation of HNCO yields [H 2 NCO] + (Δ H f 0 =672 kJ mol −1 ), whereas HCNO produces [HCNOH] + (Δ H f 0 =990 kJ mol −1 ). The proton affinity of fulminic acid, HCNO, is estimated to be 758 kJ mol −1 .

The role of hydrogen-bridged radical cations in the dissociation of ionized glycolaldehyde [HOCH2CHO]+•

Abstract Ab initio molecular orbital theory calculations combined with mass spectrometric experiments show that the dissociation of metastable glycolaldehyde radical cations occurs at the thermochemical threshold and that this process proceeds via a CHO bridged ion [CH 2 O(H)…H…CO] +• .