G4MP2, DFT and CBS-Q calculation of proton and electron affinities, gas phase basicities and ionization energies of hydroxylamines and alkanolamines
The proton affinities, gas phase basicities and adiabatic ionization energies and electron affinities of some important hydroxylamines and alkanolamines were calculated using B3LYP, CBS-Q and G4MP2 methods. Also, the B3LYP method was used to calculate vertical ionization energies and electron affinities of the molecules. The calculated ionization energies are in the range of 8-10.5 eV and they decrease as the number of carbon atoms increases. Computational results and ion mobility spectrometry study confirm that some alkanolamines lose a water molecule due to protonation at oxygen site and form cationic cyclic compounds. Effect of different substitutions on the cyclization of ethanolamine was studied theoretically. Alkanolamines and hydroxylamines have two sites, oxygen and nitrogen atoms, to accept a proton. Therefore two proton affinities are defined for these molecules. Generally, protonation of nitrogen atoms is more favorable than protonation of oxygen sites. Hence, proton affinity values are more when the molecules are protonated at nitrogen than oxygen.