Cu(II) complex formation with xylitol in alkaline solutions

Carbohydr Res. 2004 Feb 25;339(3):599-605. doi: 10.1016/j.carres.2003.12.003.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkalies / chemistry*
  • Copper / chemistry*
  • Hydrogen-Ion Concentration
  • Magnetic Resonance Spectroscopy
  • Protons
  • Solutions / chemistry
  • Spectrophotometry
  • Xylitol / chemistry*

Substances

  • Alkalies
  • Protons
  • Solutions
  • Copper
  • Xylitol