Physicochemical Properties of 1,2,3,4-Thiatriazoles

Snyder (University of Copenhagen, H. C. 0rsted Institute), private communication, 1975. 

A PM0-CND04 analysis6 of thiatriazole and several 5-substituted derivatives (R = Ph—, MeS—, NH2—, CH2=CH—) leads to the prediction that alkylation at position 4 is favored, the relative order being N-4 N-2 N-3 (see also Section III, B). Companion potential surface calculations suggest that both H+ and CHi prefer in-plane attack on the nitrogen a-lone pairs.2 Position 3 is again the least-favored attack site, in direct contradiction to experiment.6 Either the calculations are misleading or the complexity of thermodynamic versus kinetic control in the thiatriazole system has yet to be unraveled. 

Previously it was reported that infrared (IR) spectra of all TV-mono and TV-disubstituted 5-aminothiatriazoles exhibit strong bands in the 1540-1590 cm-1 range,8-10 which are believed to be due to the C=N 

4aHOMO, highest occupied molecular orbital LUMO, lowest unoccupied molecular orbital PMO, perturbation molecular orbital. 

The compounds considered to be thiatriazoline-5-thiones were later shown in fact to be 5-substituted thiatriazoles (Section V). Therefore the assignments by Rao et al.1 of ring breathing and CH out-of-plane deformations to the supposed two different systems of 4- and 5-substituted thiatriazoles all correspond to 5-substituted thiatriazoles.11 The ring breathing absorptions are found at 1320-1260, 1238-1215, 

---