We investigate proton migrations from (H2O)(n) (n = 1-3) to difructose, alpha-D-fructofuranose-beta-D-fructofuranose-2,3', using density functional theory. The proton migrations result in O-glycosidic bond cleavage. The highest transition barrier for proton migrations taking place from (H2O)(3) to difructose is 11.67 kcal mol (-1). The barriers are much lower than those for the direct breaking of a covalent bond in a difructose linkage. In addition, an autocatalysis process is also studied. An excess proton can migrate from a fructose molecule to a difructose molecule, leading to O-glycosidic bond cleavage. The transition barrier energy for this proton migration is 5.35 kcal mol (-1). (c) 2012 Elsevier B.V. All rights reserved.