Barbituric acid tautomers: DFT computations of Keto-Enol conversions, frontier molecular orbitals and quadrupole coupling constants

Harismah K., Fazeli F., Zandi H.

Department of Chemical Engineering, Faculty of Engineering, Universitas Muhammadiyah Surakarta, Surakarta, Indonesia; Department of Biology, Payame Noor University, Tehran, Iran; Department of Chemistry, Faculty of Science, University of Qom, Qom, Iran


In this work, density functional theory (DFT) computations were performed to investigate tautomeric formation processes of barbituric acid (BA). Ten tautomers were totally investigated for the purpose based on the movement of hydrogen atoms among nitrogen and oxygen atoms providing one pure keto form (BA1) and nine other keto-enol forms. The structures were optimized, and BA1 was found to be the most stable one, and both BA3 and BA7 were found to be the most unstable ones. The point was that the ring structure was broken for both BA3 and BA7, but the structure’s stability was still approved. Indeed, such serious tautomeric conversion with breaking the structure warns for using such BA bio-organic molecules for further applications, especially in pharmacy-related ones, in which side effects or byproduct synthesis might appear. Further analyses of frontier molecular orbitals features indicated the effects of such tautomerism processes on all model systems, in which more details were obtained by atomic-scale quadrupole coupling constant (Qcc). All obtained results approved significant changes of tautomers regarding molecular and atomic scale features with more or less significant effects regarding the original BA1 reference model. © 2021 by the authors.

Barbituric acid; DFT; Frontier molecular orbital; NQR; Tautomer


Biointerface Research in Applied Chemistry

Publisher: AMG Transcend Association

Volume 12, Issue 1, Art No , Page 244 – 252, Page Count

Journal Link:

doi: 10.33263/BRIAC121.244252

Issn: 20695837

Type: All Open Access, Bronze


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