Apparent equilibrium constants and calorimetric enthalpies of reaction have been measured for the following enzyme catalyzed (L-iditol 2-dehydrogenase) biochemical reactions in phosphate buffer at pHs near 7.5 and at the temperature 298.15 K D-sorbitol(aq) + NAD(ox)(aq) = D-fructose(aq) + NAD(red)(aq), L-iditol(aq) + NAD(ox)(aq) = L-sorbose(aq) + NAD(red)(aq), xylitol(aq) + NAD(ox)(aq) = D-xylulose(aq)+ NAD(red)(aq). Here, NAD(ox) is beta-nicotinamide-adenine dinucleotide (oxidized form) and NAD(red) is beta-nicotinamide-adenine dinucleotide (reduced form). The results are used to calculate equilibrium constants and standard molar enthalpies, entropies, and Gibbs free energies for reference reactions involving specific species. Standard formation properties and standard transformed formation properties of the biochemical reactants are also calculated. The thermodynamics of the xylose assimilation pathway is summarized.