Some isomers and tautomers of thiobarbital – A DFT treatment

Thiobarbital is characterized with its sedative and hypnotic properties; however it exhibits an antithyroid effect. Moreover it has a narrow range of therapeutic and toxic dose. In the present study, firstly thiobarbital and one of its structural isomer, constructed by mutual sulphur/oxygen replacements have been investigated thoroughly within the restrictions of density functional theory at the level of B3LYP/6-311++G(d,p). Secondly, its 1,3-proton tautomers have been considered at the same level of calculation. The collected data revealed that all the structures considered have exothermic heat of formation and favorable Gibbs free energy of formation values. They are thermally favored and electronically stable at the standard states. Various structural and quantum chemical data have been collected and discussed, including IR and UV-VIS spectra.