Cu(II) complex formation with xylitol in alkaline solutions.
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.
Norkus
Eugenijus
E
Laboratory of Catalysis, Institute of Chemistry, A Gostauto 9, LT-2600 Vilnius, Lithuania. norkus@ktl.mii.lt
Vaiciūniene
Jūrate
J
Vuorinen
Tapani
T
Gaidamauskas
Ernestas
E
Reklaitis
Jonas
J
Jääskeläinen
Anna-Stiina
AS
Crans
Debbie C
DC
D000468:Alkalies / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D011522:Protons; D012996:Solutions / Q000737:chemistry; D013053:Spectrophotometry; D014993:Xylitol / Q000737:chemistry*
D000468:Alkalies; D011522:Protons; D012996:Solutions; D003300:Copper; D014993:Xylitol