{"id":5684,"date":"2022-03-15T09:31:35","date_gmt":"2022-03-15T07:31:35","guid":{"rendered":"https:\/\/akki.ut.ee\/?p=5684"},"modified":"2022-03-15T09:32:41","modified_gmt":"2022-03-15T07:32:41","slug":"quantifying-acidity-in-heterogeneous-systems-biphasic-pka-values","status":"publish","type":"post","link":"https:\/\/akki.ut.ee\/en\/quantifying-acidity-in-heterogeneous-systems-biphasic-pka-values\/","title":{"rendered":"Quantifying acidity in heterogeneous systems: Biphasic pKa values"},"content":{"rendered":"<p>As a result of a recent development in our group, it is now, for the first time, possible to rigorously measure acidity of acids in biphasic systems (aqueous phase at equilibrium with a water-immiscible phase) by using biphasic p<i>K<\/i><sub>a<\/sub> values (p<i>K<\/i><sub>a<\/sub><sup>ow<\/sup> values). This work has now been published in <a href=\"https:\/\/doi.org\/10.1021\/acs.analchem.1c05510\"><i>Analytical Chemistry<\/i> <strong>2022<\/strong>, <i>94<\/i>, 4059\u20134064<\/a>.<\/p>\n<p><a href=\"https:\/\/akki.ut.ee\/wp-content\/uploads\/2022\/03\/TOC_graph.png\"><img loading=\"lazy\" decoding=\"async\" class=\" wp-image-5686 alignright\" src=\"https:\/\/akki.ut.ee\/wp-content\/uploads\/2022\/03\/TOC_graph-300x189.png\" alt=\"\" width=\"446\" height=\"281\" srcset=\"https:\/\/akki.ut.ee\/wp-content\/uploads\/2022\/03\/TOC_graph-300x189.png 300w, https:\/\/akki.ut.ee\/wp-content\/uploads\/2022\/03\/TOC_graph-1024x645.png 1024w, https:\/\/akki.ut.ee\/wp-content\/uploads\/2022\/03\/TOC_graph-768x484.png 768w, https:\/\/akki.ut.ee\/wp-content\/uploads\/2022\/03\/TOC_graph.png 1125w\" sizes=\"auto, (max-width: 446px) 100vw, 446px\" \/><\/a>In this work, the octanol-water biphasic p<i>K<\/i><sub>a<\/sub><sup>ow<\/sup> values have been determined for 35 acids of various structures and chemical properties (carboxylic acids, phenols, diphenylamines, imides, different CH acids) using UV-Vis and NMR (<sup>1<\/sup>H, <sup>13<\/sup>C, or <sup>31<\/sup>P) spectrometry.<\/p>\n<p>Biphasic p<i>K<\/i><sub>a<\/sub> values enable quantifying acid dissociation in biphasic systems in a more realistic and rigorous way than the conventional \u201cmono-phasic\u201d p<i>K<\/i><sub>a<\/sub> values. The latter completely ignores a large part of the picture \u2013 partitioning of the neutrals and the ions between the two phases and ion-pairing in the low-polarity phase. In contrast, p<i>K<\/i><sub>a<\/sub><sup>ow<\/sup> values account for these effects. The ratio of the acid and its conjugate base is measured in the 1-octanol phase, using UV-Vis and\/or NMR spectrometric method. The activity of H<sup>+<\/sup> is measured in the aqueous phase with a conventional pH-meter. The p<i>K<\/i><sub>a<\/sub><sup>ow<\/sup> values are obtained at different concentrations and extrapolated to zero concentration.<\/p>\n<p>Biphasic systems are present in many biological and technological systems and processes: cell membranes, solvent extraction, phase-transfer catalysis, sensor membranes, etc. In all such systems, acid-base properties of the participating compounds would be best described using biphasic rather than \u201cmono-phasic\u201d p<i>K<\/i><sub>a<\/sub> values.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>As a result of a recent development in our group, it is now, for the first time, possible to rigorously measure acidity of acids in biphasic systems (aqueous phase at&#8230;<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[54],"tags":[],"class_list":{"0":"post-5684","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-news"},"_links":{"self":[{"href":"https:\/\/akki.ut.ee\/en\/wp-json\/wp\/v2\/posts\/5684","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/akki.ut.ee\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/akki.ut.ee\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/akki.ut.ee\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/akki.ut.ee\/en\/wp-json\/wp\/v2\/comments?post=5684"}],"version-history":[{"count":3,"href":"https:\/\/akki.ut.ee\/en\/wp-json\/wp\/v2\/posts\/5684\/revisions"}],"predecessor-version":[{"id":5689,"href":"https:\/\/akki.ut.ee\/en\/wp-json\/wp\/v2\/posts\/5684\/revisions\/5689"}],"wp:attachment":[{"href":"https:\/\/akki.ut.ee\/en\/wp-json\/wp\/v2\/media?parent=5684"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/akki.ut.ee\/en\/wp-json\/wp\/v2\/categories?post=5684"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/akki.ut.ee\/en\/wp-json\/wp\/v2\/tags?post=5684"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}