Abstrakt
Quantum chemistry calculations were performed using the ORCA software to understand the structures and energetics of organic ions relevant to gas phase ion chemistry. Molecular geometries of a range of neutral volatile organic compound molecules and ions resulting from protonation, the addition of H3O+ and the addition of NH4+ were optimized using the B3LYP hybrid density functional theory, DFT, method.
Then the total energies and the normal mode vibrational frequencies were determined and the total enthalpies of the neutral molecules and ions were thus calculated for the standard temperature and pressure. The calculations were performed for several feasible structures of each of the ions.
It was found that the binding energies of H3O+ and NH4+ to molecules correlate with their proton affinities.