A COMPARATIVE-STUDY ON ENERGETICS AND MECHANISM OF THE ENE REACTION

The comparison between RHF and UMP2 optimizations, for the ene reactio n, indicates that RHF level calculations can reproduce the transition state geometries of the higher level of theory accurately. Also the UM P2//RHF activation energies are in very good agreement with UMP2//UMP2 results. The relatively inexpensive UMP2/6-31G//RHF/3-21G calculatio n for the reaction between propene and maleic anhydride reproduces the experimental activation energy within the experimental uncertainty. T he semiempirical AM1 method is suitable for preliminary studies of the ene reaction, but the UHF/AM1 level results should be taken with caut ion.