A computational study of the double hydrogen migration in the molecular ions of endo tricyclo[5.2.1.0 2,6]decene

Previous field ionization kinetic experiments have supported strongly that the double hydrogen migration prior to the elimination of C 5H 8 from the molecular ions of the endo isomers of 8,9-disubstituted tricyclo[5.2.1.0 2,6]decenes, which is not observed for the exo isomers, proceeds in a concerted, i.e., dyotropic way. This paper describes the results of ab initio calculations at the ROHF/4-31G and DFT level of theory, performed on the double hydrogen migration for the ionized endo isomer of unsubstituted tricyclo[5.2.1.0 2,6]decene. An intrinsic reaction coordinate calculation at the DFT level has shown indeed a direct connection between the structures of the molecular ions of the endo isomer before and after the double hydrogen migration, thus corroborating the earlier suggested concerted, i.e., dyotropic pathway of this double hydrogen rearrangement.