A DFT study of the hydrolysis of hydantoin

Abstract

AbstractDensity functional theory (DFT) calculations were made on the hydrolysis of hydantoin (2,4‐imidazolidinedione). In the neutral hydrolysis, reacting systems composed of hydantoin and (H2O)n with n = 1+3, 2+3, 3+3, and 4+3 were adopted. Three water molecules (“+3”) participate in the in‐plane hydrogen‐bond circuit, and the n–3 = 1, 2, 3 or 4 water cluster works for the out‐of‐plane nucleophilic attack onto the carbonyl carbon of hydantoin. Transition states (TSs) involving bond interchanges prompted by proton transfers were determined. The reaction path with n = 3+3 containing N‐carbamoyl glycine, N‐carboxy glycine and three tetrahedral intermediates was found to be most likely.In the acid‐catalyzed hydrolysis, a reacting system composed of hydantoin and H3O+(H2O)7 was employed. Ten TSs and nine intermediates were obtained. N‐carbamoyl glycine and N‐carboxy glycine were confirmed to be detectable stable species. The product consists of glycine, carbonic acid (not CO2), NH4+, and (H2O)5. It has the exothermic energy, whereas the product in the neutral hydrolysis is of the endothermic one for all n values. For both neutral (n = 3+3) and acid‐catalyzed hydrolyses, the rate‐determining steps were calculated to be for formation of the tetrahedral intermediate, HOOC‐CH2‐NH‐C(OH)2NH2. The pattern of proton transfers along hydrogen bonds was carefully investigated.