Chemical Properties
Alachlor is a colorless to yellow crystal chemical substance. It is soluble in most organic
solvents, but sparingly in water. Alachlor is an RUP, therefore it should be purchased and
used only by certifi ed, trained workers and plant protection applicators. The US EPA categorizes
it as toxicity class III, meaning slightly toxic. However, alachlor products bear the
signal word DANGER on their labels because of their potential to cause cancer in laboratory
animals. Alachlor is an aniline herbicide used to control annual grasses and broadleaf
weeds in fi eld corn, soybeans, and peanuts. It is a selective systemic herbicide, absorbed
by germinating shoots and roots. It works by interfering with a plant’s ability to produce
protein and by interfering with root elongation. Alachlor has extensive use as a herbicide
in the United States. It is available as granules or emulsifi able concentrate.
Definition
ChEBI: An aromatic amide that is N-(2,6-diethylphenyl)acetamide substituted by a methoxymethyl group at at the nitrogen atom while one of the hydrogens of the methyl group has been replaced by a chlorine atom.
General Description
Crystalline solid. Melting point 104-106°F (40-41°C). Used as a herbicide.
Reactivity Profile
A halogenated acetamide. Organic amides/imides react with azo and diazo compounds to generate toxic gases. Flammable gases are formed by the reaction of organic amides/imides with strong reducing agents. Amides are very weak bases (weaker than water). Imides are less basic yet and in fact react with strong bases to form salts. That is, they can react as acids. Mixing amides with dehydrating agents such as P2O5 or SOCl2 generates the corresponding nitrile. The combustion of these compounds generates mixed oxides of nitrogen (NOx).
Air & Water Reactions
Hydrolyzes under strongly acidic and strongly basic conditions.
Health Hazard
Alachlor is a slightly toxic herbicide. It causes slight to moderate degrees of skin irritation.
While a 90-day study on laboratory rats and dogs given diets containing low to moderate
amounts of alachlor (1–100 mg/kg/day) showed no adverse effects, a 1-year study indicated
that at a dose above 1 mg/kg/day, alachlor causes damage in the liver, spleen, and
kidney.
Potential Exposure
A chloracetanilide herbicide. In manufacture, formulation and application of this preemergence herbicide, personnel may be exposed. Its major use (99%) is as a preemergence herbicide for field crops (corn, soybeans, and peanuts, etc.).
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. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit. If this chemical has been inhaled, remove from exposure and transfer promptly to a medical facility
Shipping
UN2588 Pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required.
Incompatibilities
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. Corrosive to iron and steel.
Waste Disposal
This compound is hydrolyzed under strongly acid or alkaline conditions, to chloroacetic acid, methanol, formaldehyde and 2,6-diethylanilne. Incineration is recommended as a disposal procedure. Techniques for alachlor removal from potable water have been reviewed by EPA but the data revealed no superior method. Improper disposal of pesticides is a violation of federal law. Dispose In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide containers.
Agricultural Uses
Herbicide: A pre-emergence herbicide for corn, soybeans, and
peanuts, and other field crops. It is a selective systemic
herbicide, absorbed by germinating shoots and by roots. It
works by interfering with a plant's ability to produce protein and by interfering with root elongation. It is available
as granules or emulsifiable concentrate. Alachlor is used
in mixed formulations with atrazine, glyphosate, trifluralin, and imaquin. Not approved for use in the EU. A U.S.
EPA restricted Use Pesticide (RUP).
Trade name
AGIMIX® Araclor; ALAGAM®;
ALAGAN®; ALANEX®; ALAPAZ®, suspended;
ALAZINE®; ALATOX 480®; ALCLOR 48 LE®;
CHIMICHLOR®; LARIAT®; LASAGRIN®;
LASSAGRIN®; LASSO®; LASSO MICRO-TECH®;
METACHLOR®; PARTNER® Arachlor; PILLARZO®;
SANACHLOR®
Mechanism of action
Selective, systemic action absorbed by germinating shoots. Inhibition of very long chain fatty acids (VLCFA, inhibition of cell division)
Environmental Fate
Alachlor dissipates from soil mainly through volatilization, photodegradation, and biodegradation. Many metabolites have been identified; diethylaniline, detected in some soil studies, interacts rapidly with humic substances in the soil. A half-life in soil of 7-38 days has been reported. Under certain conditions, alachlor can leach beyond the root zone and migrate to groundwater.
Metabolic pathway
The metabolism of alachlor using in vitro incubations
with microsomal fractions prepared from liver and
nasal turbinate tissues of rat and mouse (m1) results
in conversion to 3,5-diethylbenzoquinone-4-imine via
the key intermediate of 2,6-diethylaniline, the formation of which requires catalysis by microsomal
arylamidases. 2,6-Diethylaniline is oxidized to 4-amino-
3,5-diethylphenol resulting in quinone imine by further
oxidation. Rat nasal tissue possesses high enzymatic
activity which can promote the formation of the
reactive quinone imine. A methylsulfide metabolite of
alachlor is shown to be a precursor to 2,6-
diethylaniline. The deposition of radioactivity in the rat
nasal tissue is more pronounced following oral
administration of the methylsulfide metabolite of
alachlor.
The extent of DNA adduct formation by alachlor
and its metabolites is used as a guide to deduce the
causal agent(s) in the carcinogenicity of this herbicide.
Metabolic studies (m2) indicate that 2-chloro-N-
hydroxymethoxymethyl-N-(2,6-diethylphenyl)-
acetamide is an intermediate in forming 2-chloro-N-
(2,6-diethylphenyl)acetamide and presumably
formaldehyde in the mouse liver microsomal mixed-
function oxidase system and in yielding O-glucuronide of 2-chloro-N-hydroxymethyl-N-(2,6-
diethylphenyl)acetamide in the urine of alachlor-treated
mice.
Incubation of alachlor in the presence of
glutathione (GSH) with the cytosolic fraction from rat,
mouse, and monkey (m3) produces the GSH
conjugate of alachlor as the initial metabolite. The
conjugation occurs through thiol displacement of the
chlorine atom of alachlor and is catalyzed by
glutathione S-transferase (GST). Kidney cell-free
preparations of rats and monkeys readily degrade the
alachlor GSH conjugate through the mercapturic acid
pathway to the corresponding cysteinylglycine,
cysteine, and N-acetylcysteine conjugates of alachlor.
Upon UV irradiation, 14/13C-alachlor is
dechlorinated and forms a number of intermediates
that retain the aromatic ring and carbonyl carbons.
These compounds include hydroxyalachlor,
norchloralachlor, 2' ,6'-diethylacetanilide, 2-hydroxy-
2' ,6' -diethyl-N-methylacetanilide, and a lactam. The
fungus transforms 98.6% of 14C-alachlor added to the
fermentation broth, and metabolism occurs
predominantly by benzylic hydroxylation of one of the
arylethyl side chains. Two major metabolites are
isomers of 2-chloro-N-(methoxymethyl)-N-[2-ethyl-6-(1-
hydroxyethyl)-phenyl]acetamide and 2-chloro-N-(2,6-
diethylphenyl)acetamide. The minor metabolite is
2-chloro-N-(methoxymethyl)-N-(2-vinyl-6-
ethlyphenyl)acetamide. N-Dealkylation by fungal
biotransformation is also observed.
Toxicity evaluation
Alachlor has a low persistence in soil, with a half-life ofz8 days.
The main means of degradation is by soil microbes. It has
moderate mobility in sandy and silty soils, and thus can migrate
to groundwater. The largest groundwater-testing program for
a pesticide, the National Alachlor Well Water Survey, was conducted
throughout the last half of the 1980s. More than sixmillion
private and domestic wells were tested for the presence of
alachlor. Less than 1% of all of the wells had detectable levels of
alachlor. In the wells in which the compound was detected,
concentrations ranged from 0.1 to 1.0 mg l-1, with themajority
having concentrations≈0.2mg l-1. Alachlor is relatively stable
to hydrolysis and photolysis in water, and degradation in water is
not considered as an important environmental fate process. Alachlor
appears to be persistent under aquifer biological and
geochemical conditions. This means that alachlor can appear in
groundwater years after use and can migrate with groundwater away from use areas. Alachlor contamination has resulted in loss
of untreated groundwater as a source of drinking water in Florida
and other states. The bioaccumulation factor in the channel
catfish is 5.8 times the ambient water concentration, indicating
that alachlor is not expected to accumulate appreciably in aquatic
organisms.
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