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Cu(II) complex formation with xylitol in alkaline solutions |
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| Authors: | Norkus Eugenijus Vaiciūniene Jūrate Vuorinen Tapani Gaidamauskas Ernestas Reklaitis Jonas Jääskeläinen Anna-Stiina Crans Debbie C |
| Affiliation: | a Laboratory of Catalysis, Institute of Chemistry, A. Goštauto 9, LT-2600 Vilnius, Lithuania b Department of Forest Products Technology, Helsinki University of Technology, Vuorimiehentie 1, FIN-02150 Espoo, Finland c Faculty of Chemistry, Vilnius University, Naugarduko 24, LT-2006 Vilnius, Lithuania d Lithuanian Customs Laboratory, Akademijos 7, LT-2021 Vilnius, Lithuania e Department of Chemistry, Colorado State University, Fort Collins, CO 80523-1872, USA |
| Abstract: | The formation of four Cu(II)-xylitol complexes was observed in aqueous alkaline solutions (11.0< or =pH< or =14.0, I=1.0, 20 degrees C) by means of direct current polarography and VIS spectrophotometry. Mononuclear hydroxy complexes, CuXyl(OH)- (log beta=17.7 +/- 0.5), CuXyl(OH)2(2-) (log beta=20.2 +/- 0.3) and CuXyl2(OH)2(4-) (log beta=22.4 +/- 0.3), are formed at high ligand-to-metal ratios (L:M> or =10), whereas dinuclear complex Cu2Xyl (log beta=29.2 +/- 0.3) is the predominant species at low ligand-to-metal ratio (L:M=0.5). Diffusion coefficients and molar absorptivities of the complex species were determined. pH variable 13C NMR suggested that pKa values of xylitol are rather similar and equal to 13.8 +/- 0.2, 13.9 +/- 0.1 and 13.9 +/- 0.2 for OH-groups adjacent to (C-1,C-5), (C-3) and (C-2,C-4) carbon atoms, respectively. |
| Keywords: | Xylitol Copper(II) Complex formation Deprotonation |
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