(117f) The Effects of Water On Sugar Reactions

Qian, X., University of Arkansas
Nimlos, M. R., National Renewable Energy Laboratory
Johnson, D. K., National Renewable Energy Laboratory

Ab initio molecular dynamics and metadynamics simulations were used to determine the free energy surfaces (FES) for the acid catalyzed β-D-glucose condensation reaction. Protonation of C1-OH on the β-D-glucose, breakage of the C1-O1 bond, and the formation of C1 carbocation is the rate-limiting step. The effects of solvent on the reaction were investigated by determining the FES both in the absence and presence of solvent water. It was found that water played a critical role in these reactions. The reaction barrier for the proton-catalyzed glucose condensation reaction is solvent induced because of proton's high affinity with water. During these simulations, β-D-glucose conversion to α-D-glucose process via the C1 carbocation was also observed. The associated free energy change and activation barrier for this reaction were determined.