Abstract
Density functional theory (DFT) at the B3LYP-6-311++G(3df, 2p)//6-311++G(d, p) level of theory in the gas phase and solution was performed to investigate the relative stabilities of all possible tautomers of 2-amino-2-oxazolin-4-one. Five different paths have been proposed to investigate the amino/oxo <-> imino/oxo proton transfer (PT) process. These paths are direct, mono-, di- and tri-water-assisted and self-assistance (dimerization) PT process. A clear catalytic effect has been observed when the introduction of water molecules and self-dimerization are taken place. Furthermore, barrier energies, equilibrium constants and reaction rate constants of the PT process between amine/oxo and imine/oxo tautomers of the self-assistance and in the presence of one, two and three water-assisted molecules were calculated. The computed activation barriers in the presence of water molecules are about 35-45 kcal/mol lower than those in the isolated case. In addition, the effective rate of the T1 <-> T2 processes were also recorded, compared and discussed. Finally, time-dependent-DFT (TD-DFT) was performed to determine the electronic absorption spectra of all species under probe. A reasonable agreement with the available experiments was also achieved.