Acylating Capacity of the Fosfotungstic Wells-Dawson Heteropoly-acid: Intermediate Reactive Species

S. COLLINS; S. MATKOVIC; A. BONIVARDI; L. BRIAND

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Lugar: Washington; Año: 2011 vol. 115 p. 700 - 709

1932-7447

The mechanism of adsorption and decomposition of acetic anhydride over phosphotungstic Wells-Dawsonheteropoly acid (HPA) was investigated through infrared spectroscopy with especially dedicated in situ cells.Both gaseous and liquid acetic anhydride dissociatively chemisorbs on the heteropoly acid, producing theintermediate acyl CH3CO+ species, adsorbed acetate species, and acetic acid. The former is known as the keyintermediate species in the Friedel-Crafts acylation reaction. Moreover, the consumption of the Brønstedacid sites observed during the adsorption and decomposition of acetic anhydride over the HPA indicates thatthose sites are the active ones of the genesis of the acyl intermediate species. Surface acetate species andacetic acid strongly adsorb on the active acid sites deactivating the heteropoly acid.