The influence of surfactants on acylation in anhydrous hydrogen fluoride

Abstract

We investigated the acylation reaction of aromatic compounds with anhydrides, acids and acid halides in the presence of anhydrous hydrofluoric acid (AHF) and anhydrous hydrofluoric acid/surfactant mixtures as catalysts. Simons et al. [Simons et al., J. Am. Chem. Soc., 61 (1939) 1795–1796] carried out these reactions in the presence of AHF in a temperature range of 80–100 °C. We investigated the acylation reactions in the presence and absence of micelle forming surfactants in AHF at room temperature. Using micelle forming surfactants like cetyltrimethylammonium bromide or cetylamine in these reactions, up to 25% increased yields of ketone have been observed. Cetylpyridinium chloride and cetyltributylammonium bromide did not lead to higher yields. A marked increase of yield has been observed at surfactant concentrations only above the cmc values in AHF [Miethchen et al, Wiss. Z. Uni. Rostock N-Reihe 39 (1990) 7/8 36–43]. The influence of reaction temperature, surfactant concentration, acylating agent and reaction time on the yield of generated ketones will be presented.