Kinetics of the ene reactions of 4-phenyl-1,2,4-triazoline-3,5-dione with β-pinene and 2-carene: Temperature, high pressure, and solvent effects

Abstract

© 2018 Wiley Periodicals, Inc. The data on temperature, solvent, and high hydrostatic pressure influence on the rate of the ene reactions of 4-phenyl-1,2,4-triazoline-3,5-dione (1) with 2-carene (2), and β-pinene (4) have been obtained. Ene reactions 1+2 and 1+4 have high heat effects: ∆Hr-n (1+2) −158.4, ∆Hr-n(1+4) −159.2 kJ mol−1, 25°C, 1,2-dichloroethane. The comparison of the activation volume (∆V≠(1+2) −29.9 cm3 mol−1, toluene; ∆V≠(1+4) −36.0 cm3 mol−1, ethyl acetate) and reaction volume values (∆Vr-n(1+2) −24.0 cm3 mol−1, toluene; ∆Vr-n(1+4) −30.4 cm3 mol−1, ethyl acetate) reveals more compact cyclic transition states in comparison with the acyclic reaction products 3 and 5. In the series of nine solvents, the reaction rate of 1+2 increases 260-fold and 1+4 increases 200-fold, respectively, but not due to the solvent polarity.