Kinetic Studies on the Strictly Catalytic Acetylation of Mesitylene with Acetic Anhydride by HCl and Metal Chlorides in Acetic Acid

Article abstract of DOI:10.1246/bcsj.54.1288

On the acetylation of mesitylene (1, 0.5-1 mol dm^-3) with acetic anhydride (Ac2O, 0.5-1.5 mol dm^-3) at 30-90 deg C in acetic acid as solvent, SbCl5, FeCl3, SnCl4, or ZnCl2 (each of 0.02-0.2 mol dm^-3) under the co-catalytic effect of HCl (O-0.75 mol dm^-3) showed a continuous catalytic activity.The product was exclusively 2',4',6'-trimethylacetophenone for conversions of 1 in the range of 0-90percent.The reaction was first order with respect to 1 and Ac2O.The rate constants were proportional to 1-1.4th power of the concentration of the metal chloride.The apparent activation energy was 18.8 kcal mol^-1 for all the catalysts.The catalytically active species are thought to be the conjugate acids from the metal chloride and HCl.Relative catalytic activities of the metal chlorides varied in parallel with their relative Lewis acid-strengths.