The Effect of Dicarboxylic Acid Catalyst Structure on Hydrolysis of Cellulose Model Compound D-Cellobiose in Water

Background: Polycarboxylic acids are of interest as simple mimics for cellulase enzyme- catalyzed depolymerization of cellulose. In this study, DFT calculations were used to investigate the effect of structure on dicarboxylic acid organo-catalyzed hydrolysis of cellulose model compound D-cellobiose to D-glucose. Methods: Binding energy of the complex formed between D-cellobiose and acid (Ebind), as well as glycosidic oxygen to dicarboxylic acid closest acidic H distance, were studied as key parameters affecting the turn over frequency of hydrolysis in water. Results: α-D-cellobiose - dicarboxylic acid catalyst down face approach showed high Ebind values for five of the six acids studied, indicating the favorability of the down face approach. Maleic, cis-1,2-cyclohexane dicarboxylic, and phthalic acids with the highest catalytic activities showed glycosidic oxygen to dicarboxylic acid acidic H distances 3.5-3.6 Å in the preferred configuration. Conclusion: The high catalytic activities of these acids may be due to the rigid structure, where acid groups are held in a fixed geometry.