Effect of Water or Ethanol on the Tautomeric Stability and Proton Transfer Reaction of all Possible Tautomers of Hydantoin: Implicit v/s Explicit Solvation

Abstract Hydantoin exhibits tautomerism and the interconversion among the tautomers was studied using theoretical methods in the gas phase and solvents (water or ethanol). The implicit solvation as well as one explicit solvent molecule with water or ethanol were investigated. The functional used was B3LYP-D3(BJ) and the basis set for all atoms was aug-cc-pVTZ. The results indicate that the electronic energy barriers in the gas phase and implicit solvation are in the range 50-90 kcal mol-1. However, explicit water is found to have a catalytic effect as the electronic energy barriers are lowered to 18-30 kcal mol-1. Explicit ethanol lowers the electronic energy barriers further by about 2 kcal mol-1. This study should be beneficial for the rational design and experiments involving hydantoin and water or ethanol as solvents.