Surface Intermediate Species of the 4-Isobutylacetophenone Adsorption-Reaction over Fosfotungstic Wells-Dawson Heteropoly Acid

SILVANA R. MATKOVIC, GRACIELA M. VALLE AND LAURA E. BRIAND

LATIN AMERICAN APPLIED RESEARCH

Universidad Nacional del Sur

Lugar: Bahia Blanca; Año: 2009 p. 173 - 178

0327-0793

Surface adsorbed species of isobuty-benzene and 4-isobutylacetophenone on bulk fosfo-tungstic Wells-Dawson acid H6P2W18O62.xH2O (HPA) have been screened in the present investiga-tion. The evolution of chemisorbed species towards products was followed through infrared spectros-copy of systems containing liquid reactants and the solid acid kept at various temperatures. 4-Isobutylacetophenone adsorbs on Brønsted acid sites of the heteropoly acid and further reacts to-wards a condensation product similarly to the reac-tion of acetophenone over other acid materials such as, mordenite, niobic acid and sulfated zirconia. The condensation product possesses well defined infrared signals at 1654 cm-1 and 1597 cm-1 that re-semble the carbonyl stretching vibration and the double bond of dypnone C6H5COHC=C(CH3)C6H5. Additional signals at 1221 cm-1 and a shoulder at 1284 cm-1 ascribed to the vibration of the C6H5 species in the C6H5COHC= group, give more evidences of the formation of a chalcone type compound. A reaction mechanism of the Aldol condensation of 4-isobutylacetophenone through an enol reactive intermediate is proposed.