Hydrogen atom addition to hydrocarbon guests in radiolyzed zeolites

The formation of H adducts during radiolysis of zeolites containing olefini c and aromatic hydrocarbon guests was demonstrated to occur by H atom trans fer from the zeolite to the adsorbed molecules. The H adducts and other par amagnetic radiolysis products (radical cations and H-loss radicals) were de tected by EPR spectroscopy. The mechanism of H adduct formation was confirm ed by, inter alia, H/D isotopic labeling and comparison of results in HZSM5 and H-Mordenite to results in their Na+-exchanged counterparts. The effect s of charge transfer among radiolysis products and zeolite-adsorbate intera ctions on the relative yields of trapped species is discussed. It is propos ed that molecules smaller that a critical size adsorb inhomogeneously in ZS M5, forming aggregates in which ion-molecule reactions occur. Interpretatio n of the experimental results was aided by quantum chemical calculations of the molecular properties of the intermediates and their reaction energetic s. This included evaluation of electron-transfer exothermicities, activatio n energies for H addition, and the relative acidities of the radical cation s.