The molecular target site of clomazone has recently
been determined. With clomazone, carotenoid synthesis
is inhibited, but no intermediates in the carotenoidcommitted
portion of the pathway accumulate (5,6).
Synthesis of the derivatives of GGPP (gibberellic acid,
phytol, carotenoids) is inhibited by clomazone (5–8).
However, the synthesis of certain sesquiterpenoids and
triterpenoids is not inhibited (9). Until recently, there was
no credible report of the effect of clomazone on any enzyme
of the terpenoid pathway (10–12). This was due to the
fact that clomazone is a proherbicide and that the proper
enzyme had not been tested.
Depending purity, it may be clear and colorless to pale yellow or brownish liquid. Commercially available as emulsifiable concentrates that can be dissolved in water
ChEBI: A oxazolidinone that is 1,2-oxazolidin-3-one substituted by a 2-chlorobenzyl group at position 2 and two methyl groups at position 4.
Moderately toxic by ingestion, inhalation,
and skin contact. A reproductive hazard.
Herbicide: Clomazone is a broad-spectrum herbicide used on
rice, peas, pumpkins, soybeans, sweet potatoes, winter
squash, cotton, tobacco and fallow wheat fields to control
annual grasses and broadleaf weeds.
CERANO®; COLZOR TRIO®;
COMMAND®; COMMENCE®, DIBEL®; FMC® 57020;
GAMBIT®; MAGISTER®; MERIT®; STRATEGY®
Causes disruption of chlorophyll and carotenes synthesis causing chlorosis of the target plants and death due to energy depletion.
1. 1000 kg of water was added to a 4000 L reactor followed by 460 kg of 4,4-dimethylisoxazolidin-3-one. The mixture was stirred for 1 hour at room temperature.
2. 383kg of sodium carbonate (Na2CO3) was added to the reaction mixture in small portions. The temperature of the mixture was raised to 85°C and the mixture was stirred continuously at this temperature for 2 hours.
3. 672 kg of o-chlorobenzyl chloride (2-chlorobenzyl chloride) was added slowly and dropwise over a period of 5 hours at 85°C. The mixture was kept at the same temperature for 2 hours. After the dropwise addition was completed, the temperature was maintained at 85°C until the reaction was complete.
4. The reaction mixture was cooled to room temperature, 800 kg of dichloromethane was added and stirred at room temperature for 15 hours.
5. The aqueous phase was separated and the aqueous phase was extracted three times with dichloromethane.
6. Recover the dichloromethane by distillation followed by addition of 2000 kg of hexane to the reactor. The mixture was refluxed for 1 hour, then cooled to 10-15 °C and continued stirring for 1 hour.
7. The solid product was separated by filtration, washed several times with hexane and finally dried under high vacuum to give pure 2-(2-chlorobenzyl)-4,4-dimethyloxazolidin-3-one (815 kg, purity: 96%).
Note: Similar results were obtained using sodium hydroxide instead of sodium carbonate as base.
Clomazone is a oxazolidione broadspectrum herbicide used on rice, peas, pumpkins, soybeans, sweet potatoes, winter squash, cotton, tobacco, and fallow wheat fields to control annual grasses and broadleaf weeds.
By the preparative incubation of clomazone with
microorganisms that have the ability to metabolize
clomazone, the metabolites are identified via major
biotransformation reactions which involve
hydroxylation at the 5-methylene carbon and one of
the 3-methyl groups of the isoxazolidone ring and at
the 3 0 -position of the phenyl ring. Minor metabolic
routes include dihydroxylation on the phenyl ring,
cleavage of the isoxazolinone ring, or complete
removal of the isoxazolinone ring to form
2-chlorobenzyl alcohol. Under aerobic conditions of
soils, degradation of clomazone proceeds primarily by
CO2 evolution and the formation of bound soil
residues. In flooded soils, clomazone is found rapidly
to degrade via the formation of the reductive product N-[(2-chlorophenyl)methyl]-3-hydroxy-2,2-
dimethylpropionamide. In tolerant soybean cell
suspension cultures, the only metabolite identified is
b-glycosyl-2-chlorobenzyl alcohol.
UN2902 Pesticide, liquid, toxic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required.
Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides.
Do not discharge into drains or sewers. Dispose of waste material as hazardous waste using a licensed disposal contractor to an approved landfill. Consult with environmental regulatory agencies for guidance on acceptable disposal practices. In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide containers. Containers must be disposed of properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office.
[1] Patent: WO2015/353, 2015, A1. Location in patent: Page/Page column 16; 17
[2] Patent: CN106749072, 2017, A. Location in patent: Paragraph 0018; 0021; 0024; 0027
