Kinetics of Diels–Alder reactions between 1,3-cyclopentadiene and isoprene

The work deals with a detailed study of the kinetics of the cycloaddition reactions between isoprene and cyclopentadiene. The laboratory experiments were carried out in a batch reactor in a cyclohexane solution at different temperatures. Measured concentrations of the reactants and 1:1 Diels–Alder adducts were fitted to the kinetic model. Kinetic parameters for formation of 5 individual isomeric codimers of cyclopentadiene and isoprene were determined. Kinetic measurements gave evidence that 5-methyl-cis-3a,4,7,7a-tetrahydro-1H-indene is formed by two reaction routes: (i) by the Diels–Alder reaction of cyclopentadiene with isoprene in which cyclopentadiene acts as a dienophile, and (ii) by the Cope rearrangement from endo-5-isopropenyl-2-norbornene, the dominant codimer. It depends on the reaction conditions which of them prevails.