The effect of solvent on a Lewis acid catalyzed Diels-Alder reaction, using computed and experimental kinetic isotope effects.

A new transition structure for the Diels-Alder reaction between isoprene and acrolein catalyzed by Et(2)AlCl is found to reconcile reported discrepancies between computed and observed secondary kinetic isotope effects (KIEs). Including the effect of solvent realigns the computed results with experiment demonstrating the importance of nonbond interactions at transition structures. Comparison of experimental and newly predicted KIE data reaffirms the ability of theory and experiment to probe the mechanism and transition structure geometry of organic reactions.