{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,26]],"date-time":"2026-08-26T12:54:25Z","timestamp":1787748865707,"version":"build-2784847793"},"reference-count":45,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2016,4,22]],"date-time":"2016-04-22T00:00:00Z","timestamp":1461283200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FWF - Austrian Science Fund","award":["V436-N34"],"award-info":[{"award-number":["V436-N34"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Crystals"],"abstract":"<jats:p>The crystal structure of the methanol hemisolvate of 5,5-dibromobarbituric acid (1MH) displays an H-bonded layer structure which is based on N\u2013H\u2219\u2219\u2219O=C, N\u2013H\u2219\u2219\u2219O(MeOH) and (MeOH)O\u2013H\u2219\u2219\u2219O interactions. The barbiturate molecules form an H-bonded substructure which has the fes topology. 5,5\u2032-Methanediylbis(5-bromobarbituric acid) 2, obtained from a solution of 5,5-dibromobarbituric acid in nitromethane, displays a N\u2013H\u00b7\u00b7\u00b7O=C bonded framework of the sxd type. The conformation of the pyridmidine ring and the lengths of the ring substituent bonds C5\u2013X and C5\u2013X\u2032 in crystal forms of 5,5-dibromobarbituric acid and three closely related analogues (X = X\u2032 = Br, Cl, F, Me) have been investigated. In each case, a conformation close to a C5-endo envelope is correlated with a significant lengthening of the axial C5\u2013X\u2032 in comparison to the equatorial C5\u2013X bond. Isolated molecule geometry optimizations at different levels of theory confirm that the C5-endo envelope is the global conformational energy minimum of 5,5-dihalogenbarbituric acids. The relative lengthening of the axial bond is therefore interpreted as an inherent feature of the preferred envelope conformation of the pyrimidine ring, which minimizes repulsive interactions between the axial substituent and pyrimidine ring atoms.<\/jats:p>","DOI":"10.3390\/cryst6040047","type":"journal-article","created":{"date-parts":[[2016,4,25]],"date-time":"2016-04-25T09:55:00Z","timestamp":1461578100000},"page":"47","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["The Hydrogen Bonded Structures of Two 5-Bromobarbituric Acids and Analysis of Unequal C5\u2013X and C5\u2013X\u2032 Bond Lengths (X = X\u2032 = F, Cl, Br or Me) in 5,5-Disubstituted Barbituric Acids"],"prefix":"10.3390","volume":"6","author":[{"given":"Thomas","family":"Gelbrich","sequence":"first","affiliation":[{"name":"Institute of Pharmacy, University of Innsbruck, Innrain 52c, 6020 Innsbruck, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Doris","family":"Braun","sequence":"additional","affiliation":[{"name":"Institute of Pharmacy, University of Innsbruck, Innrain 52c, 6020 Innsbruck, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stefan","family":"Oberparleiter","sequence":"additional","affiliation":[{"name":"Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 80, 6020 Innsbruck, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5212-9020","authenticated-orcid":false,"given":"Herwig","family":"Schottenberger","sequence":"additional","affiliation":[{"name":"Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 80, 6020 Innsbruck, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ulrich","family":"Griesser","sequence":"additional","affiliation":[{"name":"Institute of Pharmacy, University of Innsbruck, Innrain 52c, 6020 Innsbruck, Austria"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2016,4,22]]},"reference":[{"key":"ref_1","first-page":"1041","article-title":"Molecular compounds, crystalline solid solutions, and new cases of polymorphism in barbiturates. 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