Hydrogensulfate and tetrakis(hydrogensulfato)borate ionic liquids: synthesis and catalytic application in highly Brønsted-acidic systems for Friedel–Crafts alkylation
Hydrogensulfate and tetrakis(hydrogensulfato)borate ionic liquids have been synthesised and characterised. These ionic liquids are halogen-free, available from cheap raw materials and easy to prepare. They have been used as additives to sulfuric acid in the Friedel–Crafts-alkylation of benzene with 1-decene. The results clearly demonstrate an interplay of acidity and solubility effects caused by the ionic liquid additive. In some cases, low amounts of ionic liquid additive result in a dramatic improvement of product yield.