Thermodynamic and kinetic studies of the retro-Diels-Alder reaction of 1,4-cyclohexadiene, 4H-pyran 4H-thiopyran, 1,4-dioxine, and 1,4-dithiine: a theoretical investigation

Abstract

Theoretical studies of the retro-Diels-Alder reaction of 1,4-cyclohexadiene, 4H-pyran 4H-thiopyran, 1,4-dioxine, and 1,4-dithiine in the gas phase were carried out using DFT methods at the B3LYP/6–311 + G(d,p) levels of theory. The barrier height (ΔE‡) and thermodynamic parameters (ΔG‡ and ΔH‡) were estimated. The progress of the reactions was followed by means of the Wiberg bond indices. The synchronicity values of the reactions were calculated. The kinetic parameters were calculated for both reactions in 300–1200-K temperature range. Also, fitted equations to the gas phase Arrhenius equation were determined. Effect of the character and number of heteroatoms were illustrated on the thermodynamic and kinetic parameters.