{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T05:14:21Z","timestamp":1787030061823,"version":"build-2736575974"},"reference-count":65,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2024,1,12]],"date-time":"2024-01-12T00:00:00Z","timestamp":1705017600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>In order to look for the origins of tautomeric preferences in neutral creatinine in vacuo, we examined prototropic conversions for model azoles, namely mono-hydroxy and mono-amino imidazoles, and also for their selected 1-methyl derivatives. All possible isomeric forms of creatinine and model compounds, resulting from intramolecular proton transfer (prototropy), conformational isomerism about \u2013OH, and configurational isomerism about =NH, were studied in the gas phase (model of non-polar environment) by means of quantum-chemical methods. Because the bond-length alternation is a consequence of the resonance phenomenon, it was measured for all DFT-optimized structures by means of the harmonic oscillator model of electron delocalization (HOMED) index. Important HOMED analogies were discussed for investigated azoles and compared with those for previously studied cyclic azines, including pyrimidine nucleic acid bases. The internal effects were taken into account, and the stabilities of the investigated tautomers-rotamers were analyzed. Significant conclusions on the favored factors that can dictate the tautomeric preferences in creatinine were derived.<\/jats:p>","DOI":"10.3390\/sym16010098","type":"journal-article","created":{"date-parts":[[2024,1,12]],"date-time":"2024-01-12T07:47:16Z","timestamp":1705045636000},"page":"98","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["On Some Origins of Tautomeric Preferences in Neutral Creatinine in Vacuo: Search for Analogies and Differences in Cyclic Azoles and Azines"],"prefix":"10.3390","volume":"16","author":[{"given":"Ewa Daniela","family":"Raczy\u0144ska","sequence":"first","affiliation":[{"name":"Department of Chemistry, Warsaw University of Life Sciences (SGGW), ul. Nowoursynowska 159c, 02-776 Warszawa, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,1,12]]},"reference":[{"key":"ref_1","first-page":"184","article-title":"Prototropic Tautomerism of Heterocycles: Heteroaromatic Tautomerism\u2014General Overview and Methodology","volume":"76","author":"Elguero","year":"2000","journal-title":"Adv. Heterocycl. Chem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"3561","DOI":"10.1021\/cr030087h","article-title":"Tautomeric Equilibria in Relation to pi-Electron Delocalization","volume":"105","author":"Gawinecki","year":"2005","journal-title":"Chem. Rev."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"157","DOI":"10.1016\/S0065-2725(00)76005-3","article-title":"The Tautomerism of Heterocycles: Five-Membered Rings with Two or More Heteroatoms","volume":"76","author":"Minkin","year":"2006","journal-title":"Adv. Heterocycl. 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