{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,22]],"date-time":"2025-11-22T18:45:28Z","timestamp":1763837128481},"reference-count":21,"publisher":"Wiley","issue":"4","license":[{"start":{"date-parts":[[2015,12,14]],"date-time":"2015-12-14T00:00:00Z","timestamp":1450051200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"DOI":"10.13039\/100000001","name":"National Science Foundation","doi-asserted-by":"publisher","award":["CHE-1048703","CHE 1263154"],"award-info":[{"award-number":["CHE-1048703","CHE 1263154"]}],"id":[{"id":"10.13039\/100000001","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Angew Chem Int Ed"],"published-print":{"date-parts":[[2016,1,22]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>The thermodynamically stable enol crystal form of barbituric acid, previously prepared as powder by grinding or slurry methods, has been obtained as single crystals by slow cooling from methanol solution. The selection of the enol crystal was facilitated by a density\u2010gradient method. The structure at 224 and 95\u2005K confirms the enol inferred on the basis of powder data. The enol has bond lengths that are consistent with the expected bond order and with DFT calculations that include treatment of hydrogen bonding. In isolation, the enol is higher in energy than the tri\u2010keto form by 50\u2005kJ\u2009mol<jats:sup>\u22121<\/jats:sup> which must be more than compensated by enhanced hydrogen bonding. Both crystal forms have four normal H\u2010bonds; the enol has two additional H\u2010bonds with O\u2013O distances of 2.49\u2005\u00c5. Conversion into the enol form occurs spontaneously in the solid state upon prolonged storage of the commercial tri\u2010keto material. Slurry conversion of tri\u2010one to enol in ethanol is reversed in direction in ethanol\u2010D<jats:sub>1<\/jats:sub>.<\/jats:p>","DOI":"10.1002\/anie.201508078","type":"journal-article","created":{"date-parts":[[2015,12,14]],"date-time":"2015-12-14T13:51:30Z","timestamp":1450101090000},"page":"1309-1312","source":"Crossref","is-referenced-by-count":16,"title":["Single\u2010Crystal X\u2010ray Diffraction Structure of the Stable Enol Tautomer Polymorph of Barbituric Acid at 224 and 95\u2005K"],"prefix":"10.1002","volume":"55","author":[{"given":"Madalynn G.","family":"Marshall","sequence":"first","affiliation":[{"name":"Department of Chemistry, 1-014 Center for Science &amp; Technology Syracuse University  Syracuse NY 13244-4100 USA"},{"name":"Syracuse University &amp; Department of Chemistry Iowa State University  1605 Gilman Hall Ames IA 50011-3111 USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Valerie","family":"Lopez\u2010Diaz","sequence":"additional","affiliation":[{"name":"Department of Chemistry, 1-014 Center for Science &amp; Technology Syracuse University  Syracuse NY 13244-4100 USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bruce S.","family":"Hudson","sequence":"additional","affiliation":[{"name":"Department of Chemistry, 1-014 Center for Science &amp; Technology Syracuse University  Syracuse NY 13244-4100 USA"},{"name":"Syracuse University &amp; Department of Chemistry Iowa State University  1605 Gilman Hall Ames IA 50011-3111 USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2015,12,14]]},"reference":[{"key":"e_1_2_2_1_1","doi-asserted-by":"publisher","DOI":"10.1039\/C0CE00123F"},{"key":"e_1_2_2_2_1","doi-asserted-by":"publisher","DOI":"10.1021\/cg200970t"},{"key":"e_1_2_2_3_1","doi-asserted-by":"publisher","DOI":"10.1002\/chem.200902485"},{"key":"e_1_2_2_4_1","doi-asserted-by":"publisher","DOI":"10.1107\/S0365110X63000438"},{"key":"e_1_2_2_5_1","doi-asserted-by":"publisher","DOI":"10.1021\/cg034209a"},{"key":"e_1_2_2_6_1","doi-asserted-by":"publisher","DOI":"10.1107\/S0365110X61002539"},{"key":"e_1_2_2_7_1","doi-asserted-by":"publisher","DOI":"10.1107\/S0567740877006839"},{"key":"e_1_2_2_8_1","doi-asserted-by":"publisher","DOI":"10.1021\/cg049661o"},{"key":"e_1_2_2_9_1","doi-asserted-by":"publisher","DOI":"10.1002\/anie.201101040"},{"key":"e_1_2_2_9_2","doi-asserted-by":"publisher","DOI":"10.1002\/ange.201101040"},{"key":"e_1_2_2_10_1","unstructured":"\u201cMethod and apparatus for separation of pharmaceutical materials on the basis of their density\u201d:B. S.Hudson J.Melton U.S. Patent US 9 089 850 B2 (28 July 2015."},{"key":"e_1_2_2_11_1","doi-asserted-by":"crossref","first-page":"611","DOI":"10.1515\/zkri-2015-1845","volume":"230","author":"Bek\u00f6 S. L.","year":"2015","journal-title":"Z. Kristallogr."},{"key":"e_1_2_2_12_1","unstructured":"C4H4N2O3 FW 128.09 0.6\u00d70.05\u00d70.05\u2005mm3 monoclinic P21\/n Z=4 0.71073\u2005\u00c5 X-ray. At 224(2)\u2005K:a=4.8497(3) b=8.9134(6) c=11.8920(8)\u2005\u00c5 \u03b1=90 \u03b2=94.892(2) \u03b3=90\u00b0 V=512.19(6)\u2005\u00c53 1.661\u2005Mg\u2009m\u22123 \u03bc=0.145\u2005mm\u22121 \u03b8max=27.221\u00b0 11\u2009272 reflections (1139 independent) Rint=0.0316 finalRindices [I>2sigma(I)] R1=0.0335 wR2=0.0933 Rindices (all data) R1=0.0399 wR2=0.0991 largest diff. peak and hole 0.206 and \u22120.239\u2005e\u2009\u00c5\u22123 full-matrix least-squares refinement onF2 data\/restraints\/parameters 1139\/0\/85 goodness-of-fit onF2=1.048. CCDC\u20051418712contains the supplementary crystallographic data for this paper. These data can be obtained free of charge fromThe Cambridge Crystallographic Data Centre. At 95\u2005K:a=4.7799(4)\u2009 b=8.9363(8)\u2009 c=11.8023(11)\u2005\u00c5 \u03b1=90 \u03b2=96.133(3) \u03b3=90\u00b0 V=501.25(8)\u2005\u00c53 V=1.697\u2005Mg\u2009m\u22123 \u03bc=0.148\u2005mm\u22121 \u03b8max=27.397\u00b0 11\u2009533 reflections collected (1130 independent) Rint=0.0208 finalRindices [I>2sigma(I)] R1=0.0306 wR2=0.0801 Rindices (all data) R1=0.0344 wR2=0.0832 largest diff. peak and hole 0.273 and \u22120.255\u2005e\u2009\u00c5\u22123 full-matrix least-squares refinement onF2 data\/restraints\/parameters 1130\/0\/85 goodness-of-fit onF2=1.079. CCDC\u20051418693contains the supplementary crystallographic data for this paper. These data can be obtained free of charge fromThe Cambridge Crystallographic Data Centre."},{"key":"e_1_2_2_13_1","first-page":"12","volume-title":"An Introduction to Hydrogen Bonding","author":"Jeffrey G. A.","year":"1997"},{"key":"e_1_2_2_14_1","doi-asserted-by":"publisher","DOI":"10.1002\/1521-3773(20020104)41:1<48::AID-ANIE48>3.0.CO;2-U"},{"key":"e_1_2_2_14_2","doi-asserted-by":"publisher","DOI":"10.1002\/1521-3757(20020104)114:1<50::AID-ANGE50>3.0.CO;2-H"},{"key":"e_1_2_2_15_1","doi-asserted-by":"publisher","DOI":"10.1021\/j100197a027"},{"key":"e_1_2_2_16_1","first-page":"558","author":"Hafner G. Kresse and J.","journal-title":"Phys. Rev. B 47"},{"key":"e_1_2_2_17_1","unstructured":"Sigma\u2013Aldrich product number 11709 lot S72013-029 specification date 2008. The 50\u2005gram sample was stored on a laboratory shelf and infrequency opened until 2012 when it was used in a course that involved Raman microscopy studies of the solid material. The spectra observed were those reported in the supplementary materials for Ref.\u2005[8] with and without the strong C=O stretching mode changing from one to the other when the region being examined was changed from one particle to another. In some cases the particles showed a demarcation line that had one or the other spectrum on either side of that line."},{"key":"e_1_2_2_18_1","doi-asserted-by":"publisher","DOI":"10.1021\/cg800524d"},{"key":"e_1_2_2_19_1","doi-asserted-by":"publisher","DOI":"10.1021\/cg5014973"}],"container-title":["Angewandte Chemie International Edition"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.1002%2Fanie.201508078","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.1002%2Fanie.201508078","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/anie.201508078","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/full-xml\/10.1002\/anie.201508078","content-type":"application\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"http:\/\/api.wiley.com\/onlinelibrary\/chorus\/v1\/articles\/10.1002%2Fanie.201508078","content-type":"application\/pdf","content-version":"am","intended-application":"syndication"},{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/anie.201508078","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,10,6]],"date-time":"2023-10-06T18:16:38Z","timestamp":1696616198000},"score":1,"resource":{"primary":{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/10.1002\/anie.201508078"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2015,12,14]]},"references-count":21,"journal-issue":{"issue":"4","published-print":{"date-parts":[[2016,1,22]]}},"alternative-id":["10.1002\/anie.201508078"],"URL":"https:\/\/doi.org\/10.1002\/anie.201508078","archive":["Portico"],"relation":{},"ISSN":["1433-7851","1521-3773"],"issn-type":[{"value":"1433-7851","type":"print"},{"value":"1521-3773","type":"electronic"}],"subject":[],"published":{"date-parts":[[2015,12,14]]}}}