Formation of spiroiminodihydantoin due to the reaction between 8-oxoguanine and carbonate radical anion: A quantum computational study

Reaction of 8-oxoguanine (8OG) with carbonate radical anion (CO3·−) producing spiroiminodihydantoin has been investigated using density functional theory. Geometries of reactant complex, intermediate complexes, product complexes and transition states were optimized at the B3LYP/6-31G(d,p) level of theory in gas phase which was followed by single point energy calculations employing the B3LYP, M06-2X and WB97XD functionals along with the AUG-cc-pVDZ basis set in gas phase and aqueous media. Solvent effect was treated employing the integral equation formalism of the polarizable continuum model. Possible roles of aeration, stirring and photoirradiation of reaction media which are performed in experimental studies have been explained.