Abstract: We reported both the open-chain and closed-ring ethene cation radicals derivatives formation on pretreated H-ZSM-5 studied by ESR techniques and the use of colnputer simulations at various stages to understand the details of chemical reactions inside the three-dimensional channels of the zeolite. The comparison of these four related open chain cation radicals with two related closed ring cyclopentene and cyclohexene canon radicals shows that the unequivalent β-proton hyperfine splittings in the 2,3-dimethyl-2-hexene cation radicals can be understood by the contact of these canon molecules within the three-dimensional pore structure. Thus, we use the computer simulations to help us correct assignment of the isotropic proton hyperfine splittings on the surface as well as to study both the intramolecular hindered torsional motions of the solid-gas interactions and ion-molecule reactions.
A new equation relating the observed proton hyperfine splitting to the non-planar structure of the cation radicals is proposed. The equation is supported by the basic symmetry principle as well as our experimental results.

Key words: Alkene cation radicals, H-ZSM-5 zeolites, ESR, Non-planar conformations, A new spin density relationship