Catalysis by Heteropoly Compounds. XIII. An Infrared Study of Ethanol and Diethyl Ether in the Pseudoliquid Phase of 12-Tungstophosphoric Acid

Abstract

Ethanol, diethyl ether, and water absorbed in, and their thermal desorption from, the pseudoliquid phase of 12-tungstophosphoric acid have been studied by means of infrared spectroscopy. For all three molecules, the state of the absorption of 6 molecules per anion, H3PW12O40·6R2O (R; C2H5 or H), was quite stable and the secondary structures were similar. The intensities of the C–H vibrations indicated that the methyl group of the ethanol molecules interacted with the anions and that its interaction became stronger as the amount of absorbed molecules decreased. In the thermal desorption of absorbed ethanol or diethyl ether, a protonated monomer and dimer as well as an ethoxy group were detected by means of infrared spectroscopy. These species are reaction intermediates of the dehydration of ethanol which were assumed previously (J. Am. Chem. Soc., 109, 5535 (1987)). It was also found that, upon the dehydration of H3PW12O40·6H2O, the proton which had been hydrogen-bonded to the oxygen atom of the water molecule ((H2O)2H+) migrated onto the bridging oxygen of the heteropoly anion (PW12O4O403−).