An international collaboration of scientists has formulated a commonly used weed-killer as an ionic liquid to reduce its environmental impact. Research published in Green Chemistry describes how the scientists have created a less volatile and less water soluble form of the herbicide dicamba, by making a liquid salt of its deprotonated form.
Dicamba is used to control broadleaf weeds in grain fields and grasslands, among other areas. It can affect the environment though water runoff from sprayed fields and volatisation through spraying and evaporation from areas where it has been applied.
Chemically, dicamba consists of a benzene ring carrying a carboxylic acid group. It is generally applied in its free acid form. To overcome the problem of volatisation, a team of scientists from the US and Poland formed a series of ionic liquid formulations of dicamba, using the deprotonated acid as the anion.
They formulated and tested 28 new dicamba ionic liquids using hydrophobic cations with surfactant or antimicrobial activities. The new ionic liquids showed lower volatility, increased thermal stability and improved efficacy over the parent dicamba in field tests, whilst the hydrophobicity of the ionic liquids decreased the water solubility of the herbicide to reduce the environmental impacts of water run-off.
O A Cojocaru et al, Green Chem., 2013.