Kinetic variations in acid-catalyzed monosaccharide conversion

Kinetic models for the conversion of abundant carbohydrates have often remained controversial. Direct spectroscopic observations show that conversion of ketoses by Lewis acidic salts follows an exponential time course, while the corresponding conversion of aldoses follows a second order kinetics in various solvents and using various metal chloride catalysts. Bronsted acid catalyzed conversion of glucose and fructose displays two kinetic regimes due to the competition between the kinetically favored formation of anhydrosugars and the thermodynamically favored formation of furanics. Thus, slow kinetic phases occur towards the end of glucose conversion by Lewis and Bronsted acidic catalysis, albeit for different reasons.