Interactions of D-cellobiose with p-toluenesulfonic acid in aqueous solution: a 13C NMR study

The effects of adding D2SO4, and p-toluenesulfonic acid-d to D-cellobiose dissolved in D2O were investigated at 23 °C by plotting 13C NMR chemical shift changes (Δδ) against the acid to D-cellobiose molar ratio. 13C Chemical shifts of all 18 carbon signals from α and β anomers of D-cellobiose showed gradual decreases due to increasing acidity in aqueous D2SO4 medium. The C-1 of the α anomer showed a slightly higher response to increasing D+ concentration in the surrounding. In the aqueous p-toluenesulfonic acid-d medium, C-6′ and C-4′ carbons of both α, and β anomeric forms of D-cellobiose are significantly affected by increasing the sulfonic acid concentrations, and this may be due to a 1:1 interaction of p-toluenesulfonic acid-d with the C-6′, C-4′ region of the cellobiose molecule.