A study of the metal binding capacity of saccharinic acids formed during the alkali catalysed decomposition of cellulosic materials: nickel complexation by glucoisosaccharinic acids and xyloisosaccharinic acids.
The stoichiometry of the metal complexes formed between nickel and the ligand β-glucoisosaccharinic acid (β-GISA) and a racemic mixture of enantiomers of xyloisosaccharinic acid (XISA) has been determined at both neutral and alkaline pHs. Bjerrum plots, Job's plots and conductance measurements indicated that for each of the systems one to one Ni(ligand) complexes were formed at near neutral pHs (<7.5). At intermediate alkaline pHs (7.5-13) there is evidence to support the formation and precipitation of Ni2(ligand)(OH)3 complexes, finally, at high pH (>13) sparingly soluble Ni2(ligand)(OH)4 complexes were formed. The stability constants for the Ni(β-GISA), Ni(α-GISA) and Ni(XISA) complexes formed at neutral pH were determined under identical conditions using polarographic studies. The measured stability constants for Ni(β-GISA) (log10 β = 1.94 ± 0.15) and for Ni(α-GISA)(log10 β = 2.07 ± 0.13) are very similar; the value measured for the Ni(XISA) complex (log10 β = 0.83) was an order of magnitude smaller. The stability constants for the Ni2(Ligand)(OH)4 complexes formed at highly alkaline pHs were determined using the Schubert method. The measured stability constant for Ni2(β-GISA)(OH)4 (log10 β = 30.6 ± 0.5) was an order of magnitude bigger than the value for Ni2(α-GISA)(OH)4 (log10 β = 29.0 ± 0.5) measured under identical conditions. Attempts to measure the stability constant for Ni2(XISA)(OH)4 were unsuccessful; Ni2(XISA)(OH)4 complexes were not present in significant amounts at high pH to allow the log10β value to be determined by the Schubert method.
Department of Chemical Sciences, School of Applied Sciences, University of Huddersfield, Queensgate, Huddersfield, West Yorkshire, HD1 3DH, UK.
Michael
M
Almond
Department of Chemical Sciences, School of Applied Sciences, University of Huddersfield, Queensgate, Huddersfield, West Yorkshire, HD1 3DH, UK.
Daniel
D
Belton
Department of Biological Sciences, School of Applied Sciences, University of Huddersfield, Queensgate, Huddersfield, West Yorkshire, HD1 3DH, UK.
Paul N
PN
Humphreys
Department of Chemical Sciences, School of Applied Sciences, University of Huddersfield, Queensgate, Huddersfield, West Yorkshire, HD1 3DH, UK. Electronic address: a.p.laws@hud.ac.uk.
Andrew P
AP
Laws
D056831:Coordination Complexes / Q000737:chemistry; D005947:Glucose / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009532:Nickel / Q000737:chemistry*; D013237:Stereoisomerism; D013400:Sugar Acids / Q000737:chemistry*; D014994:Xylose / Q000737:chemistry
D056831:Coordination Complexes; D013400:Sugar Acids; D009532:Nickel; D014994:Xylose; D005947:Glucose
Alpha-glucoisosaccharinic acid; Beta-glucoisosaccharinic acid; ISA; Metal complexation; Stability constant; Xyloisosaccharinic acid