In acidic aqueous solutions the xylonic acid/xylonate equilibrium is coupled with the formation of the γ- and δ-lactones. The γ-lactone is formed more readily, whereas the δ-lactone can only be observed in traces at very low pH values (<2.5). By means of 13C NMR, both the lactone hydrolization constant and the acid dissociation constant could be determined (KL = 4.08, = 3.65 ± 0.34). Further, a second deprotonation of one of the hydroxyl groups could be observed at very high pH ( = 13.3 ± 0.76).
- Xylonic acid
Hummel, M., Leppikallio, M., Heikkinen, S., Niemelä, K., & Sixta, H. (2011). Acidity and lactonization of xylonic acid: A nuclear magnetic resonance study. Journal of Carbohydrate Chemistry, 29(8-9), 416-428. https://doi.org/10.1080/07328303.2011.567424