KINETIC-STUDIES OF THE REACTIONS OF KETOSES AND ALDOSES IN WATER AT HIGH-TEMPERATURE .3. MECHANISM OF FORMATION OF 2-FURALDEHYDE FROM D-XYLOSE

The literature records two alternative hypotheses for the mechanism of dehydration of xylose to 2-furaldehyde (furfural), namely (1) a succession of reactions proceeding mainly via open-chain intermediates, and (2) an acid-catalyzed sequence proceeding through a 2,5-anhydride intermediate. The existing evidence for hypotheses (1) and (2) is reviewed and found to favor (2). The major products from xylose in water at 250-degrees (with and without acid catalysis) have been investigated on a time-resolved basis. A kinetic model based on the second hypothesis is found to be consistent with the experimental data; whereas kinetic models based on the first hypothesis do not fit the data.