Theoretical study on the reaction mechanisms of the aldol-condensation of 5-hydroxymethylfurfural with acetone catalyzed by MgO and MgO+

The reaction mechanisms and the turnover frequencies of the aldol-condensation of 5-hydroxymethylfurfural (HMF) with acetone catalyzed by the neutral MgO and the cationic MgO+ have been theoretically investigated at B3LYP/6-311++G(d,p) level, using the polarizable continuum model in aqueous solution at the temperature of 326K. The aldol-condensation of HMF with acetone catalyzed by the neutral MgO or the cationic MgO+ is thermodynamically favorable. The reaction mechanism involves the crucial reaction steps of H-shift and C-C bond formation, while the rate-determining step is concerned to the H-shift. The Lewis acidity of the cationic MgO+ makes it exhibit better catalytic performance than the neutral MgO. Water, as a bridge in the H-shift, interacts with both the neutral MgO and the cationic MgO+ moieties, leading to the Bronsted basicity, and then promoting the catalytic performance both of the neutral MgO and the cationic MgO+. Both the Lewis acidity and Bronsted basicity of active sites can enhance the catalytic performance in the aldol-condensation of HMF with acetone. (C) 2014 Elsevier B.V. All rights reserved.