Nuclear Magnetic Resonance Studies of the Arrangement of Benzene Molecules in the Cavities of the Zeolite NaX

The second moments of the proton resonances of benzene in the cavities of a zeolite NaX with Si/Al = 1.32 have been measured for C6H6and C6H3D3, between 100 K and 200 K, and the intra‐ and intermolecular contribution extracted from the results. From the intramolecular contribution for coverages above four molecules in a large cavity below 150 K a rotation around the hexagonal axis of the benzene molecule can be concluded. For the explanation of the intermolecular contribution, model calculations have been carried out, showing that for four molecules in a large cavity the molecules are arranged flat on the walls above the S2‐sites with a distance of about 0.32 nm from the ions in these sites. The intermolecular second moment for a coverage above five molecules in a cavity can be explained only by arranging the fifth molecule in the window between two cavities parallel to the plane of the window. This arrangement explains the limiting coverage of about six molecule in a large cavity as well as the possibility of a motion of the molecules at higher temperatures.