{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,31]],"date-time":"2025-10-31T07:37:32Z","timestamp":1761896252697,"version":"build-2065373602"},"reference-count":15,"publisher":"Wiley","issue":"3","license":[{"start":{"date-parts":[[2016,2,25]],"date-time":"2016-02-25T00:00:00Z","timestamp":1456358400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia (FCT)","award":["SFRH\/BPD\/72652\/2010","SFRH\/BPD\/84805\/2012"],"award-info":[{"award-number":["SFRH\/BPD\/72652\/2010","SFRH\/BPD\/84805\/2012"]}]},{"name":"Fundo Europeu de Desenvolvimento Regional (FEDER)","award":["Program PT2020","007265-UID\/QUI\/50006\/2013"],"award-info":[{"award-number":["Program PT2020","007265-UID\/QUI\/50006\/2013"]}]}],"content-domain":{"domain":["chemistry-europe.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["ChemistryOpen"],"published-print":{"date-parts":[[2016,6]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>The rearrangement between isomers 6\u2010 and 8\u2010bromo\u2010apigeninidin (<jats:bold>6<\/jats:bold> and <jats:bold>8<\/jats:bold>) was studied by pH jumps using stopped flow, UV\/Vis, NMR, and HPLC analysis. The system constitutes a pH\u2010dependent network of chemical reactions involving up to 18\u2005different species. The dynamic network is equivalent to a single diprotic acid exhibiting two p<jats:italic>K<\/jats:italic><jats:sub>a<\/jats:sub>s, 2.55 and 5.4. Similar to other flavylium derivatives, the mole fraction of the species hemiketal and <jats:italic>cis<\/jats:italic>\u2010chalcone in both multistate isomers are negligible at the equilibrium. At pH\u20051, the pure isomers are slowly converted in a mixture containing about 50\u2009% of isomers <jats:bold>6<\/jats:bold> and <jats:bold>8<\/jats:bold>, while at pH\u20054, the system evolves to mixture of 10\u2009% <jats:italic>trans<\/jats:italic>\u2010chalcone and 90\u2009% of quinoidal bases. A series of pH jumps from pure isomer <jats:bold>6<\/jats:bold> at pH\u20051 to pH\u20056 and back to pH\u20051 leads to the same initial absorption spectra of the pure isomer <jats:bold>6<\/jats:bold>. The same occurs for pure isomer <jats:bold>8<\/jats:bold>, showing the lack of communication between the <jats:italic>cis<\/jats:italic>\u2010chalcones, at least in the time scale of few minutes. A pH jump from the equilibrated mixture of the isomers at pH\u20051.0 to 5.8 permits to follow a very slow isomerization.<\/jats:p>","DOI":"10.1002\/open.201500210","type":"journal-article","created":{"date-parts":[[2016,2,26]],"date-time":"2016-02-26T04:43:50Z","timestamp":1456461830000},"page":"236-246","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Extending the Study of the 6,8 Rearrangement in Flavylium Compounds to Higher pH Values: Interconversion between 6\u2010Bromo and 8\u2010Bromo\u2010apigeninidin"],"prefix":"10.1002","volume":"5","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2226-0404","authenticated-orcid":false,"given":"Lu\u00eds M.","family":"Cruz","sequence":"first","affiliation":[{"name":"Laborat\u00f3rio Associado para a Qu\u00edmica Verde (LAQV), Rede de Qu\u00edmica e Tecnologia (REQUIMTE) Departamento de Qu\u00edmica e Bioqu\u00edmica Faculdade de Ci\u00eancias Universidade do Porto  Rua do Campo Alegre, 687 4169-007 Porto Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0121-3695","authenticated-orcid":false,"given":"Nuno M.","family":"Bas\u00edlio","sequence":"additional","affiliation":[{"name":"Laborat\u00f3rio Associado para a Qu\u00edmica Verde (LAQV), Rede de Qu\u00edmica e Tecnologia (REQUIMTE) Departamento de Qu\u00edmica Faculdade de Ci\u00eancias e Tecnologia Universidade Nova de Lisboa  2829-516 Caparica Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0586-2278","authenticated-orcid":false,"given":"Victor A.","family":"de\u2005Freitas","sequence":"additional","affiliation":[{"name":"Laborat\u00f3rio Associado para a Qu\u00edmica Verde (LAQV), Rede de Qu\u00edmica e Tecnologia (REQUIMTE) Departamento de Qu\u00edmica e Bioqu\u00edmica Faculdade de Ci\u00eancias Universidade do Porto  Rua do Campo Alegre, 687 4169-007 Porto Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0528-1967","authenticated-orcid":false,"given":"Jo\u00e3o C.","family":"Lima","sequence":"additional","affiliation":[{"name":"Laborat\u00f3rio Associado para a Qu\u00edmica Verde (LAQV), Rede de Qu\u00edmica e Tecnologia (REQUIMTE) Departamento de Qu\u00edmica Faculdade de Ci\u00eancias e Tecnologia Universidade Nova de Lisboa  2829-516 Caparica Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8529-6848","authenticated-orcid":false,"given":"Fernando J.","family":"Pina","sequence":"additional","affiliation":[{"name":"Laborat\u00f3rio Associado para a Qu\u00edmica Verde (LAQV), Rede de Qu\u00edmica e Tecnologia (REQUIMTE) Departamento de Qu\u00edmica Faculdade de Ci\u00eancias e Tecnologia Universidade Nova de Lisboa  2829-516 Caparica Portugal"}]}],"member":"311","published-online":{"date-parts":[[2016,2,25]]},"reference":[{"key":"e_1_2_6_1_1","doi-asserted-by":"publisher","DOI":"10.1021\/jf049653f"},{"key":"e_1_2_6_2_1","doi-asserted-by":"publisher","DOI":"10.1021\/jf00102a002"},{"key":"e_1_2_6_3_1","doi-asserted-by":"publisher","DOI":"10.1107\/S056774087400505X"},{"key":"e_1_2_6_4_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1750-3841.2012.02668.x"},{"key":"e_1_2_6_5_1","doi-asserted-by":"publisher","DOI":"10.1055\/s-2003-40982"},{"key":"e_1_2_6_6_1","doi-asserted-by":"publisher","DOI":"10.1016\/S0040-4020(01)92086-1"},{"key":"e_1_2_6_7_1","doi-asserted-by":"publisher","DOI":"10.1021\/jf00117a017"},{"key":"e_1_2_6_8_1","doi-asserted-by":"publisher","DOI":"10.1021\/ja00390a033"},{"key":"e_1_2_6_9_1","doi-asserted-by":"publisher","DOI":"10.1039\/C1CS15126F"},{"key":"e_1_2_6_10_1","doi-asserted-by":"publisher","DOI":"10.1021\/ja00447a012"},{"key":"e_1_2_6_11_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.tet.2014.09.051"},{"key":"e_1_2_6_12_1","doi-asserted-by":"publisher","DOI":"10.1021\/jf900759q"},{"key":"e_1_2_6_13_1","doi-asserted-by":"publisher","DOI":"10.1021\/jo01039a027"},{"key":"e_1_2_6_14_1","unstructured":"H. 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