Calculation of Vibrational Spectra of p-Ethylbenzenesulfonic Acid Hydrates

Quantum-chemical calculations of vibrational spectra of the sulfonated ion-exchanger model p-ethylbenzenesulfonic acid hydrated by 1–10 water molecules and its dimer were calculated by the non-empirical SCF MO LCAO method with the 6-31G(d) basis set. The calculated results were compared with experimental IR and Raman spectra of sulfonated ion exchangers. The infl uence of hydration on the vibrational frequencies of functional groups in the ion exchangers was analyzed. It was shown that the sulfonic acid was completely dissociated if three and more water molecules per functional group were present. Bands near 1130 cm–1 were due to S–O–H bending vibrations in the absence of water molecules and C–S–O–H3O combination vibrations with 3–6 water molecules per sulfonic acid.