Vibrational spectra of molecules on zeolites. IV. Raman spectra of cyclopropane on zeolites X

Abstract

Laser Raman spectra are reported for cyclopropane adsorbed on cation- exchanged zeolites X. The results have been interpreted in terms of an edge-on interaction of the cyclopropane molecule with the zeolitic cation site. The symmetry of cyclopropane, when adsorbed on LiX and NaX, appears to be lowered from the free-molecule symmetry (D_3h) to C_2V as evidenced by the splitting of the E' mode (v₁₁) of cyclopropane. In contrast to the previously reported case of the adsorption complexes, MX+C₂H₂ and MA+C₂H₂, the adsorption interaction appears to follow a direct polarizing-power dependence on the zeolitic cation. Force- constant calculations support an interpretation based on a cation- induced dipole interaction.