PROXIMITY, PHOTOCHEMICAL REACTIVITY, AND INTERMOLECULAR H-1-C-13 CROSS-POLARIZATION IN BENZOPHENONE-D(10) AND CYCLOHEXANE IN THE ZEOLITE NAX

The photochemistry, photophysics, and solid-state C-13 CPMAS NMR of be nzophenone and cyclohexane in the zeolite NaX have been analyzed to in vestigate their proximity, relative mobility, and intermolecular react ivity. Photochemical irradiation of benzophenone in pure cyclohexane y ields benzopinacol and benzhydrol as the predominant products. In cont rast, irradiation in the solid state leads to l-cyclohexyl-l,1-dipheny lmethanol as the only product by collapse of the radical pair formed a fter hydrogen abstraction from cyclohexane by excited benzophenone. Ph osphorescence analysis at 77 K suggests a highly polar environment, bu t lack of emission at 300 K in the presence of cyclohexane is assigned to triplet decay via an efficient hydrogen abstraction reaction. Spec tral analysis by C-13 CPMAS NMR reveals that benzophenone and cyclohex ane are adsorbed in an approximate 1:2 ratio. Changes observed in spin ning and static samples before and after photolysis are interpreted in terms of molecular motions that are capable of affecting the spectral line width. That benzophenone and cyclohexane share the zeolite super cages in a close packed arrangement was shown by a relatively efficien t H-1-C-13 intermolecular cross polarization from cyclohexane to benzo phenone-d(10). Comparison of the CPMAS intensities measured with deute rated and nondeuterated benzophenone samples under identical condition s suggest that intermolecular C-D ... H-R distances between carbon ato ms of deuterated benzophenone and hydrogens of cyclohexane have an ave rage value of ca. 2.2 Angstrom.