ESR Studies of Alkyl Radicals Adsorbed on Porous Vycor Glass

Abstract

Publisher Summary Numerous properties have been used to characterize the surfaces of solids, but few have been as useful as electron spin resonance spectroscopy (ESR). ESR has been effective in elucidating the active surface sites, as well as the surface reactions. Hydrocarbons are involved in a variety of reactions and the alkyl radical is a primary intermediate in many such reactions. The alkyl radical is usually the first product in the pyrolysis and combustion of hydrocarbons. Such radicals have been detected and stabilized in glasses at low temperatures and on surfaces at low and ambient temperatures. The properties of such radicals, their formation, detection, and reactions are discussed in the chapter. The earliest ESR study of the CH 3 and C 2 H 5 radicals was reported by Gordy and McCormick who investigated the X-ray decomposition of CH 3 and C 2 H 5 compounds of zinc, mercury, and tin at 77 K. The role of mercury as a photosensitizer when coadsorbed on the surface requires clarification. This can be readily tested by using mercury-free vacuum lines in comparison with doped mercury on the surface. The tumbling frequency determination must be resolved with respect to the second-order splitting.