Hydrolysis and interactions of d-cellobiose with polycarboxylic acids

Abstract

The hydrolysis of cellulose model compound d-cellobiose was studied with a series of eight common polycarboxylic acids and two monocarboxylic acids in aqueous medium using 0.500 mmol -COOH/L at 170 °C. The maleic acid showed the highest catalytic activity with turnover frequency (TOF) of 29.5 h−1. The interaction of carboxylic acids with d-cellobiose in DMSO‑d6 was studied by determination of the pseudo first-order rate constant kH of anomeric -OH exchange rate in cellobiose using 1H NMR spectroscopy. The maleic, oxalic and citric acids showed infinitely large kH values indicating very strong interactions with d-cellobiose. The next highest interactions were found with phthalic acid (kH = 248.8 Hz). The FT-IR studies showed significant carboxylic acid C=O stretching frequency shifts (ΔνC=O) of 12, 13 and 10 cm−1 for maleic, oxalic and acetic acids respectively in mixtures with d-cellobiose.