Description
Carfentrazone is a herbicide, normally applied as the ethyl variant, used to control a wide range of broadleaved weeds. It is not expected to be persistent in the environment. Little data is available for the acid regarding its ecotoxicology or impacts on environmental health.
Chemical Properties
Pure product is viscous yellow liquid. m.p.-22.1°C, relative density 1.457 (20°C), vapor pressure 1.6×10-5Pa (25°C), partition coefficient 3.36, solubility in water 12μg/L (20°C), 22μg/L (5°C). The half-life in soil is only a few hours.
Uses
Carfentrazone is a triazolone herbicide used in the protection of grain and vegetable crops from weeds.
Definition
ChEBI: 2-chloro-3-{2-chloro-5-[4-(difluoromethyl)-3-methyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]-4-fluorophenyl}propanoic acid is a member of the class of triazoles that is 2,4-dihydro-3H-1,2,4-triazol-3-one which is substituted at positions 2, 4, and 5 by 5-(2-carboxy-2-chloroethyl)-4-chloro-2-fluorophenyl, difluoromethyl, and methyl groups, respectively. It is a member of triazoles, a member of monochlorobenzenes, a member of monofluorobenzenes and a monocarboxylic acid.
Production Methods
Carfentraone is usually prepared as the ethyl ester and its commercial follows the route typical of aryl triazolinone herbicides, constructing the triazolinone heterocycle and then attaching the aryl and ethyl ester moieties in controlled steps. Industrial routes generally begin with preparation of a chlorinated or fluorinated benzoic acid derivative, which is then coupled to a hydrazine based intermediate to form the triazolinone ring system through cyclisation and oxidation. Subsequent esterification with ethanol yields the ethyl ester that defines the commercial active ingredient. The process emphasises tight control of halogenation, moisture exclusion, and purification to maintain the required isomeric and impurity profile for herbicide registration and formulation.
Mechanism of action
Contact, absorbed by foliage with limited translocation. Inhibition of protoporphyrinogen oxidase (PPO) - cell membrane disruption
Metabolic pathway
14C-Carfentrazone is more readily absorbed by the
foliage of soybean than by weeds, with 56, 7, and
10% of the applied radioactivity recovered from the
foliage of soybean, ivyleaf morning glory, and
velvetleaf, respectively. Soybean metabolizes
carfentrazone more rapidly than weeds, with 28% of
the parent compound remaining in the treated tissue
of soybean and 48 and 67% in ivyleaf morning glory
and velvetleaf, respectively. All species accumulate
similar amounts of the free acid derivative of
carfentrazone which is the only identified metabolite.
Since both carfentrazone and the free acid are potent
inhibitors of protoporphyrinogen oxidase, the result
indicates that the tolerance of soybean to
carfentrazone may be attributed to its better ability to
metabolize carfentrazone to unidentified metabolites,
relative to weeds.
Pesticide Type
Herbicide; Metabolite
