Fig. 3.
Distortion/interaction–activation strain analysis for the Diels–Alder reactions of ethylene with cyclopentadiene and 5,5-dimethylcyclopentadiene (A), and 2,3-diazacyclopentadiene and 5,5-dimethyl-2,3-diazacyclopentadiene (B). The analysis was carried out along the intrinsic reaction coordinate (IRC) defined by the average distance of the forming bonds in Ångstroms. (Solid lines: Electronic energies; Short dashed lines: Distortion energies; Long dashed lines: Interaction energies).