High-pressure influence on the rate of diels-alder cycloaddition reactions of maleic anhydride with some dienes

The rate constants for temperature and pressure range, enthalpy, entropy, and volume of activation and reaction were measured in toluene solution for the Diels-Alder cycloaddition reaction of maleic anhydride (1) with a very active diene, 9,10-dimethylanthracene (4), and with a very inactive diene, 9-phenylanthracene (6), which is less reactive in the reaction with 1 by five orders of magnitude. Reaction rates under pressure up to 2600 bar were measured by using a high-pressure optical cell, adjusted to a UV-spectrophotometer. The volume of reaction was determined by two independent methods: by the difference of the partial molar volumes of the reactants and by the dependence of a specific volume of solution on the adduct concentration during the reaction. All parameters of activation and reaction were discussed. © 2013 Wiley Periodicals, Inc