Direct and solvent-assisted thione-thiol tautomerism in 5-(thiophen-2-yl)-1,3,4-oxadiazole-2(3H)-thione: Experimental and molecular modeling study

- The molecule exists in the thione form in the solid state.
- FT-IR and NMR data support the thione form.
- The anti-thione conformer has the lowest energy.
- The barrier height increases with increasing polarity of the solvent.
- Multiple methanol or water-assisted thione-thiol tautomerism may happen.