Sulfonamide derivatives have been widely incorporated in different types of studies, particularly in bioorganics and medicinal chemistry. Molecular conformation or tautomeric forms of molecules are directly related to their pharmaceutical and biological activities. In the scope of this work two possible tautomeric forms of 3-amino-4-[4-(dimethylamino)phenyl]-4,5-dihydro-1,2,5-thiadiazole 1,1-dioxide (C10R14N4O2S) molecule were tried to be identified by employing infrared and nuclear magnetic resonance spectroscopic methods. Obtained spectroscopic results suggest that 3-amino-4-[4-(diniethylamino)phenyl]-4,5-dihydro-1,2,5-thiadiazole 1,1-dioxide in its powder form shows the traces of both conformers (amino and imino) while in its liquid state in deuterated dimethyl sulfoxide it is mainly in imino form. (C) 2016 Elsevier B.V. All rights reserved.