Theoretical Study of the Interaction of Cu+ with 5-Methyl Hydantoin in the Gas Phase

Relative tautomerisation energies, enthalpies, entropies, Gibbs free energies, and dipole moments for the interactions of the 5-methyl hydantoin with Cu⁺ have been studied in the gas phase using hybrid density functional at the B3LYP level of theory using 6-311+(d,p) with full geometry optimization. Final energies were obtained at 6-311+(2df,2p) level. It has been found that the direct association of Cu⁺ occurs at the oxygen atom attached to position 2, which corresponds to the global minimum of the potential energy surface. For the enolic structure, the most stable one corresponds to tautomer 3a that can be formed by the 1,3-hydrogen transfer at the oxygen atom attached to position 4. Moreover, the isomerization processes leading from the most stable adduct to the other stable conformers were also investigated. The finding concluded that the Cu⁺ association has a clear catalytic effect on the tautomerization processes which connect the oxo form with enol tautomer.

Keywords: Hydantoin; Copper; Density functional calculations; Tautomerization; Gas-Phase reactivity; Carbonyl group;