Diels–Alder Reaction as an Indicator of Internal and External Factors Influencing the Rate and Equilibrium: Kinetics, Thermochemistry, Catalysis, and High Pressure. A Review

The Diels–Alder reaction (DAR), in addition to its enormous synthetic potential, is the most reliable testing ground for quantitative research of the influence of various internal and external factors on the rate and equilibrium. The influence of the energy of intermolecular orbital interaction and then the influence of the enthalpy of reaction have been considered. It has been demonstrated that the DAR rate can be described when both factors are considered jointly. Kinetic and thermochemical data for DAR in the presence of Lewis acids are discussed. New data on the DAR rate during grinding reagents in the solid phase generate many problems for further study. Finally, the analysis of extensive data on the high pressure effect on the DAR rate and equilibrium have allowed the conclusion that differences in activation volumes and reaction volumes are not related to the mechanism of the DAR.