Quantum mechanical studies of environmental effects on biomolecules
SCFab initio computations have been performed on the structure, molecular potential and hydration scheme of thiourea in view of a comparison
with urea and more generally as a model of the conjugated S=CNH-group as compared to O=CNH-. In contrast to the carbonyl oxygen,
both σ and π acceptor, the sulfur atom of the thiocarbonyl is a σ donor but a π acceptor and this results in an enhancement
of the double-bond character of thiourea. The CN bond is less attractive for a proton than urea. The hydration scheme indicates
a maximum number of four water molecules directly bound to thiourea.