Analytical Sciences

Abstract − Analytical Sciences, 19(3), 455 (2003).

11B NMR Study of p-Carboxybenzeneboronic Acid Ions for Complex Formation with Some Monosaccharides
T. M. Bulbul ISLAM, Kazuo YOSHINO,  and Akinobu SASANE
Department of Chemistry, Faculty of Science, Shinshu University, Asahi, Matsumoto 390-8621, Japan
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.