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The principal components of the carbonyl carbon chemical shift tensor of the hydrogen-bonded 1:1 stoichiometric acetone-H-ZSM-5 adsorption complex have been determined from an analysis of 13 C NMR spectra of static and magic angle sample spinning powder samples at 78 and 130 K, respectively. In a similar manner the principal elements of this tensor have been determined for physisorbed acetone in silicalite and the pure solid in order to separate changes due to hydrogen bonding of the acetone molecule in the zeolite complex from confinement effects defined as interactions of the adsorbed molecule with the siliceous cavity. The energetics associated with such changes have also been measured using microcalorimetry. The differential heats of adsorption of acetone adsorbed in H-ZSM-5 and silicalite over a wide range of surface coverage are reported. The results are compared with ab-initio calculations of the reaction of acetone with model zeolite structures to form a stoichiometric hydrogen-bonded cluster-molecule complex. At the Hartree-Fock level the agreement with respect to both energetics and isotropic shifts is good but only fair for the shielding anisotropy. The magnitudes of the chemical shifts due simply to confinement of the acetone molecule are of the same order of magnitude as those associated with hydrogen bonding.

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The dynamics associated with the adsorption complex formed by CH 3 CN at Brønsted sites in the high-silica zeolite H-MFI have been explored using 1 H, 2 H, and 13 C nuclear magnetic resonance (NMR) spectra measured as a function of temperature between 78 and 400 K. A simple NMR line-shape theory, based on rapid, smallangle reorientations of the CH 3 CN molecular axis with a temperature-dependent amplitude, has been used to account for the data. An anisotropic, angular motion is observed with a small amplitude at low temperatures increasing to approximately (35°from its average position at room temperature. This motion is primarily constrained to a plane in the zeolite, but a distribution in amplitudes for different types of sites is required to fully account for the data. At higher temperatures, the powder line shapes are completely motionally narrowed, presumably due to exchange between physisorbed molecules and those bound to the sites.