Vibrational spectra of molecules on zeolites. Part 3.—Raman spectra of pyrazine on zeolites X

Abstract

Laser Raman spectra of pyrazine on a series of alkali and alkaline earth cation exchanged X-type zeolites have been recorded. Within both the uni- and divalent cation series Raman line shifts on adsorption follow a direct cation polarizing power dependence. The observation that these line shifts are similar for zeolites incorporating uni- and divalent cations is in contrast with data for pyridine on similar surfaces. These differences between adsorbed pyrazine and pyridine have been interpreted in terms of the electronic properties of the former. For pyrazine on NaX, KX, CsX and MgX a line at ∼ 1154 cm^–1 has been assigned to a CH bending mode which is Raman inactive for the free (D_2h) molecule.