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Tautomeric preferences and electron delocalization in biurets, thiobiurets, and dithiobiurets: An ab initio study
Author(s) -
Adane Legesse,
Bharatam Prasad V.
Publication year - 2008
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.21629
Subject(s) - tautomer , chemistry , ab initio , intramolecular force , computational chemistry , quantum chemistry , ab initio quantum chemistry methods , biuret test , hydrogen bond , enol , crystallography , stereochemistry , crystal structure , molecule , organic chemistry , urea , supramolecular chemistry , catalysis
In several literature reports biuret and its sulfur analogs are reported to exist in their diketo form with general formula H 2 NCXNHCYNH 2 (X = O, Y = O, biuret; X = Y = S, dithiobiuret; and X = O, Y = S, thiobiuret). On the other hand, recently reported results on the electronic structure of biguanide analogs (X = Y = NH)demonstrated that a form equivalent to diketo is not the preferred structure. Thus, a systematic ab initio study on the tautomeric preferences of biuret and its sulfur analogs (dithiobiuret and thiobiuret) has been carried out. The results indicate that an interplay of conjugative stabilization and intramolecular hydrogen bonding to play a role in tautomeric preferences. Energy and geometric parameters, natural bond orbital analyses have been employed to understand the chemistry of the title compounds. The results indicate that unlike biguanides, these compounds prefer diketo forms containing hydrogen on the bridging nitrogen (N4) and in a trans‐ arrangement (1a–4a). However, tautomerization of these keto forms to the corresponding enol isomers was also found to be highly probable. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008