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11B NMR study of p-carboxybenzeneboronic acid ions for complex formation with some monosaccharides
T M Bulbul Islam1, Kazuo Yoshino, Akinobu Sasane
1Department of Chemistry, Faculty of Science, Shinshu University, Asahi, Matsumoto 390-8621, Japan.
Abstract:
The 11B NMR spectra of p-carboxybenzeneboronic acid (PCBA) ions demonstrated that their chemical shifts depend on the pH. At a lower pH, PCBA exists as a mixture of neutral PCBA and the monoanion with a trigonal structure, and at higher pH as the dianion with a tetrahedral structure. In the intermediate pH region, both the mono- and dianion coexist. The pKa of the monoanion of PCBA has been estimated to be 8.53. The complex formation constants of PCBA with several monosaccharides suggest that PCBA-fructose complex is most predominant.
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