RELATIVE REACTIVITIES of SUGARS IN the FORMATION of 5-HYDROXYMETHYLFURFURAL IN SUGAR-CATALYST MODEL SYSTEMS

Model systems were employed to determine the relative reactivity of sucrose, glucose, and fructose in the formation of 5-hydroxymethylfurfural (5-HMF) at pH 3.5. Fructose was the major reactant for formation of 5-HMF. Fructose was 31.2 times faster than glucose, whereas sucrose was 18.5 times faster than glucose in the rate of 5-HMF formation when averaged over three different sugar-catalyst systems. Accelerating effects of citric acid, minerals (calcium, magnesium, and potassium), and amino acids (alanine, aspartic acid, and γ-aminobutyric acid) in the formation of 5-HMF from sugars were evaluated. With fructose as the substrate, 5-HMF formed 5 times faster in the presence of citric acid and minerals than in the presence of HCl. Varying catalytic effects were noted with the three amino acids. Rates of 5-HMF formation from glucose and sucrose showed slight enhancement in the presence of the amino acids, whereas virtually no enhancement occurred when fructose was the substrate.