Synthesis of Symmetric Ethers Using Monocationic and Dicationic Acidic Ionic Liquids

Abstract

A series of monocationic and dicationic -SO3H functionalized Brønsted acidic ionic liquids (BAILs) are synthesized using different amines int.al., N,N,N′,N′-tetramethylethylenediamine, 1-methylimidazole, pyridine and alkylating agents 1,3-propane- and 1,4-butanesultones. The Hammett acidity (H0) and thermal properties by TG-DSC techniques are investigated. These ionic liquids have been applied to catalyze the dehydration reaction of aliphatic long chain alcohols (1-heptanol, 1-octanol, 1-decanol) at 195 °C. The optimization of reaction conditions and use of dicationic ionic liquids allow to reach rather high yields of symmetric diheptyl ether and dioctyl ether. The reusability of ionic liquids is evaluated using monocationic [PyPS][HSO4], dicationic [TMEDAPS][HSO4] ionic liquids and 1-heptanol.