Chlortoluronorchlorotoluron are the common names[3] for an organic compound of the phenylurea class of herbicides used to control broadleaf and annual grass weeds in cereal crops.
In 1952, chemists at E. I. du Pont de Nemours and Company patented a series of arylurea derivatives as herbicides. Several compounds covered by this patent were commercialized as herbicides: monuron (4-chlorophenyl), diuron (3,4-dichlorophenyl) and chlortoluron, the 3-chloro-4-methylphenyl example.[4][5] Subsequently, over thirty related urea analogs with the same mechanism of action reached the market worldwide.[6]
As described in the du Pont patent, the starting material is a substituted aryl amine, an aniline, which is treated with phosgene to form its isocyanate derivative. This is subsequently reacted with dimethylamine to give the final product.[4]
The phenylurea class of herbicides including chlortoluron are inhibitors of photosynthesis. They block the QBplastoquinone binding site of photosystem II, preventing electron flow from QA to QB.[7] This interrupts the photosynthetic electron transport chain and kills the plant.[8]
Chlortoluron was first licensed for use in the European Union in 1994[9] and this has been extended, currently until October 2021.[10] It is now mainly used in mixture with other herbicides including diflufenican and pendimethalin.[11]
^ abUS patent 2655445, Todd C.W., "3-(Halophenyl)-1-methyl-1-(methyl or ethyl) ureas and herbicidal compositions and methods employing same", issued 1953-10-13, assigned to E. I. du Pont de Nemours & Co.
