Pendimethalin

Chemical properties

Brown Solid

Chemical properties

Yellow-orange crystalline solid. Mild nut-like odor. Commercial product is available as an emulsifiable concentrate.

The Uses of Pendimethalin

Herbicide used to control the spread of weedgrass.

The Uses of Pendimethalin

Herbicide.

The Uses of Pendimethalin

used to control many annual grasses and broad-leaved weeds in crops such as corn, cotton, peanuts, potatoes, rice, sorghum, sunflower and tobacco.

Definition

ChEBI: A member of the class of substituted anilines that is N-(pentan-3-yl)aniline bearing two additional nitro substituents at positions 2 and 6 as well as two methyl substituents at positions 3 and 4. A herbicide used to control most annual rasses and many annual broad-leaved weeds.

General Description

Orange-yellow crystals. Non corrosive. Used as an herbicide.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

A dinitroaniline derivative.

Agricultural Uses

Herbicide: Pendimethalin is a selective pre-emergence and post-emergence herbicide used on various agricultural and non-agricultural sites to control broadleaf weeds and grassy weeds in crops such as apricot, carrot, cherry, corn, cotton, fig, garbanzos, garlic, olive, onion, nectarine, peach, pear, pecan, plum, rice and prune, and noncrop areas. It is applied to soil preplant, pre-emergence, and post-emergence with ground and aerial equipment.

Trade name

AC 92553®; ACCOTAB®; BULLET® (pendimethalin + cyanazine); GO-GO-SAN®; HERBADOX®; PAY-OFF®; PENOXALIN®; PENOXALINE®; PROWL®; SIPAXOL®; SQUADRON® (with imazaquin); STOMP®; TATA PANIDA®; VALOR®; WAY-UP®

Potential Exposure

Pendimethalin is a selective preemergence and postemergence 2,6-dinitroaniline herbicide used on various agricultural and non-agricultural sites to control broadleaf weeds and grassy weeds in crops such as apricot, carrot, cherry, corn, cotton, fig, garbanzos, garlic, olive, onion, nectarine, peach, pear, pecan, plum, rice and prune, and noncrop areas. It is applied to soil preplant, pre-emergence, and postemergence with ground and aerial equipment.

Environmental Fate

Biological. In an in vitro study, the soil fungi Fusarium oxysporum and Paecilomyces varioti degraded pendimethalin to N-(1-ethylpropyl)-3,3-dimethyl-2-nitrobenzene-1,6- diamine and 3,4-dimethyl-2,6-dinitroaniline. The latter compound was the only metabolite identified by another soil fungus; namely, Rhizoctonia bataticola (Singh and Kulshrestha, 1991)
Kole et al. (1994) studied the degradation of pendimethalin by an unadapted strain of Azotobacter chroococcum Beijerinck in pure culture condition. Degradation was rapid — 45 and 55% of the parent compound was degraded after 10 and 20 days, respectively.
xylidine. At the C-3 position on the parent compound, the methyl group oxidized to -CH2OH which underwent partial reduction of the 2-nitro group and N-dealkylation followed by oxidative cyclization to give 2-methyl-4-nitro-5-N-(1-cyclopropyl)-6-nitrosobe
Soil/Plant. In soil, the 4-methyl group on the benzene ring is oxidized to a hydroxy group which undergoes further oxidation to the carboxylic acid. The major plant metabolite is 4-(1-ethylpropyl)amino-2-methyl-3,5-dinitrobenzyl alcohol (Hartley and Kidd, 1987). Kulshrestha and Singh (1992) investigated the influence of soil moisture and microbial activity on the degradation of pendimethalin in a sandy loam soil. In both nonsterile, nonflooded and flooded soils, degradation followed first-order kinetics. The observed halflives in flooded and nonflooded conditions in nonsterile and sterile soils were 33 and 45; 52 and 67 days, respectively. In the nonsterile, nonflooded soil, pendimethalin underwent N-dealkylation and reduction of the less hindered nitro group affording N-(1-ethylpropyl)- 3,4-dimethyl-2-nitrobenzene-1,6-diamine and 3,4-dimethyl-2,6-dinitroaniline as major products. Under flooded conditions, only one degradation product was formed: N-(1- ethylpropyl)-5,6-dimethyl-7-nitrobenzimidazole. Under flooded conditions, pendimethalin was completely degraded after 4 days (Kulshrestha and Singh, 1992)
The reported half-lives of pendimethalin in a Sharkey clay soil and Bosket silt loam are 6 and 4 days, respectively (Savage and Jordan, 1980).

Metabolic pathway

Irradiation of pendimethalin in methanol yields, in addition to the minor dealkylated product, the major products 2-amino-6-nitro-N-(1-ethylpropyl)-3,4-xylidine and 2-nitroso-6-nitro-3,4-xylidine. Pendimethalin degrades rapidly through reductive cyclization of the amino group and adjacent N-ethylpropyl to give a cyclized benzimidazole product. The photodecomposition of pendimethalin involves oxidative dealkylation, nitro reduction, and cyclization. By soil bacteria, pendimethalin degrades through different pathways from the photodegradation reaction, resulting in benzimidazole and hydroxylated products of the N-alkyl and xylyl methyl groups. The major metabolic routes of pendimethalin by rats involves hydroxylation of the 4-methyl and the N-ethyl group, oxidation of these alkyl groups to carboxylic acids, nitro reduction, cyclization, and conjugation in the urine and the tissues. Products of cyclization reactions giving methylbenzimidazole-carboxylic acids are unique metabolites to the liver and kidney.

Shipping

UN3077 Environmentally hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required.

Incompatibilities

Reacts with oxidizers, acids and alkaline materials. Contact with strong oxidizers may cause fire and explosions.

Waste Disposal

It is the responsibility of chemical waste generators to determine if a discarded chemical is classified as a hazardous waste. See 40 CFR Parts 261.3 for United States Environmental Protection Agency guidelines for the classification determination. Additionally, in order to ensure complete and accurate classification, waste generators must consult state and local hazardous waste regulations. Organic pesticides, whether of botanical or synthetic origin, can be destroyed by incineration equipped with scrubbers to remove acid wastes.