Ab initio study of the tautomerism of 2,5-substituted diazoles

Abstract

Detailed investigation of the tautomerism of oxadiazoles, thiadiazoles, and selenadiazoles containing hydroxy, mercapto, or selenyl groups in position 2 and 5 of the five-membered ring was carried out at MP2, MP4, and CCSD(T) levels of theory. The relative stabilities of the tautomers of the heterocycles were investigated in gas phase. It is found that the dioxo form is the preferred tautomer if the exocyclic group is hydroxy. If the exocyclic group is mercapto or selenyl group the most stable tautomer is the mixed mercapto/thione or selenyl/selone form. The barriers of intramolecular proton transfer are too large and tautomerization should not occur.

1,3,4‐Thiadiazolidine‐2,5‐dione: Crystal Structure, Calculation of Aromaticity and Photodecomposition Quantum Yield

“…The distance between the layers is 3.10 Å. In this context, it should be mentioned that Enchev and Angelove reported an ab initio study of the tautomerism of 1 (Figure ) and similar molecules, and it was concluded that tautomer 1a is preferred over 1b in accordance with our findings.…”

Synthesis, Characterization, and Antioxidant, Antimicrobial and Toxic Properties of Novel Δ2 -1,3,4-thiadiazoline and Δ2 -1,3,4-selenadiazoline Derivatives

“…38 Appearance of medium to weak bands at the range 582-524 cm -1 in IR spectrum can be related to stretching of 𝝊(C-Se) for the compounds (Z 3 A'-Z 3 C'). 39 1 HNMR and 13…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline

“…In the theoretical by Enchev and Angelova [261], the tautomerism of oxadiazole, thiadiazole, and selenadiazole containing hydroxy, mercapto, or selenyl groups in positions 2 and 5 of the five-membered ring was investigated.…”