Herbicidal ionic liquid with dual functions has been synthesized and characterized (properties, chemical stability and biological activity). 2-Chloroethyltrimethylammonium (4-chloro-2-methylphenoxy)acetate prepared in an alkaline environment undergoes the reaction of dehydrochlorination by the E2 mechanism. This may be described as a specific instance of providing third generation ILs with high potential of application, which preserve both pesticidal properties: the herbicidal activity due to their anions and plant growth inhibition effect due to their cations. (C) 2013 Elsevier Ltd. All rights reserved.