Brønsted acidic ionic liquid 1-methylimidazolium tetrafluoroborate: a green catalyst and recyclable medium for esterification

Esterification of carboxylic acids with alcohols could be carried out in a Brønsted acidic ionic liquid 1-methylimidazolium tetrafluoroborate ([Hmim]+BF4−). Good yields were obtained, and the esters produced could be easily separated from the reaction mixture without any volatile organic solvents. The ionic liquid [Hmim]+BF4− could be reused after removal of water.