Glucose and fructose hydrates in aqueous solution by IR spectroscopy.
In the mid-infrared attenuated total reflectance (MIR-ATR) spectra of aqueous d-glucose and d-fructose solutions, two hydrates were found by factor analysis (FA) for each sugar, d-glucose penta- and dihydrates and d-fructose penta- and monohydrates. We obtained the spectra and abundances for these hydrates as a function of carbohydrate concentrations. The biggest difference in these spectra lies in the CO stretch region. From the distribution of the species, the equilibrium between d-glucose pentahydrate and dihydrate is 3(H2O)2+2(C6H12O(6).2H2O) right arrow over left arrow 2(C6H12O(6).5H2O), with the equilibrium constant KG=(3.2+/-0.6)x10(-5) L3 mol-3. For d-fructose, the equilibrium is between pentahydrate and monohydrate, 2(H2O)2+C6H12O6.H2O right arrow over left arrow C6H12O(6).5H2O, with the equilibrium constant KF=(7.1+/-1.2)x10(-3) L2 mol-2. The four hydrates are present only in aqueous solutions and cannot be obtained in the solid state.
Max
Jean-Joseph
JJ
Département de chimie-biologie, Université du Québec à Trois-Rivières, Trois-Rivières, QC, Canada G9A 5H7. jjmax@itfoptical.com
Chapados
Camille
C
D005632:Fructose / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry*; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D013055:Spectrophotometry, Infrared / Q000379:methods; D014867:Water / Q000737:chemistry
D012996:Solutions; D014867:Water; D005632:Fructose; D005947:Glucose