Chemical Properties
Brown Solid
Uses
Herbicide used to control the spread of weedgrass.
General Description
Orange-yellow crystals. Non corrosive. Used as an herbicide.
Air & Water Reactions
Insoluble in water.
Reactivity Profile
A dinitroaniline derivative.
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.
First aid
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
15 minutes, occasionally lifting upper and lower lids. Seek
medical attention immediately. If this chemical contacts the
skin, remove contaminated clothing and wash immediately
with soap and water. Seek medical attention immediately.
If this chemical has been inhaled, remove from exposure,
begin rescue breathing (using universal precautions) if
breathing has stopped, and CPR if heart action has stopped.
Transfer promptly to a medical facility. When this chemical
has been swallowed, get medical attention. Give large
quantities of water and induce vomiting. Do not make an
unconscious person vomit. Do not induce vomiting when
formulations containing petroleum solvents are ingested
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.
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.
Production Methods
Pendimethalin is commercially produced through a multi-step chemical synthesis that typically begins with the nitration of aromatic compounds, followed by amination and alkylation reactions to form the dinitroaniline structure characteristic of the herbicide. The process involves precise control of reaction conditions to ensure high purity and yield, often using solvents and catalysts to facilitate the transformations.
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®
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.
