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Three Competitive Transition States at the Glycosidic Bond of Sucrose in Its Acid-Catalyzed Hydrolysis
journal contribution
posted on 2016-02-19, 17:37 authored by Shinichi Yamabe, Wei Guan, Shigeyoshi SakakiThe acid-catalyzed hydrolysis of sucrose to glucose and
fructose was investigated by DFT calculations. Protonations to three
ether oxygen atoms of the sucrose molecule, A, B, and (C, D), were compared. Three
(B, the fructosyl-ring oxygen protonation; C, protonation to the bridge oxygen of the glycosidic bond for the
glucosyl-oxygen cleavage; and D, protonation to that
for the fructosyl-oxygen cleavage) gave the fragmentation. Paths B, C, and D were examined by the
use of the sucrose molecule and H3O+(H2O)13. The path B needs a large activation
energy, indicating that it is unlikely. The fragmentation transition
state (TS1) of path C needs almost the same activation
energy as that of path D. The isomerization TS of Int(C) → Int(D), TS(C → D), was also obtained as a bypass route. The present calculations
showed that the path via the fructosyl-oxygen cleavage (D) is slightly (not absolutely) more favorable than that via the glucosyl-oxygen
cleavage (C).