Metalaxyl
Synonym(s):N-(2,6-Dimethylphenyl)-N-(methoxyacetyl)-DL -alanine methyl ester
- CAS NO.:57837-19-1
- Empirical Formula: C15H21NO4
- Molecular Weight: 279.33
- MDL number: MFCD00055447
- EINECS: 260-979-7
- SAFETY DATA SHEET (SDS)
- Update Date: 2024-10-28 16:48:35
What is Metalaxyl?
Description
As an important fungicide group, acylanilides have a longer history than triazoles. Metalaxyl (44) is one of the most important fungicides in the group. It originates from the class of herbicidal chloroacetanilides, particularly metolachlor (45). Metolachlor, having a chiral carbon center and a chiral axis, is composed of four stereoisomers, the most herbicidally active one of which is the (αR, 1S)-isomer (32). For the stereoselective synthesis of this isomer, novel iridium-ferrocenyldiphosphine catalysts for the enantioselective hydrogenation of N-(2-ethyl-6-methylphenyl)- N-(1-methoxymethyl)-ethylidene-amine are reported. In the most effective approach, the catalyst is generated in situ from [Ir(cod)Cl]2(cod = cyclooctadiene) and the ferrocenyldiphosphine ligand (R)-(S)-PPF-P(3,5-xyl)2 (46) (33).When the substrate to catalyst ratio is 106, the conversion is complete in 2 to 3 h, producing metolachlor in optical yields over 80% (34).
Chemical properties
Pale Beige Solid
Chemical properties
Combustible, white crystalline solid or powder. Odorless.
The Uses of Metalaxyl
Metalaxyl is used for the control of air-borne pathogens by foliar application and of soil-borne pathogens by soil application on a wide range of crops. It is particularly useful against Oomycetes including soil-borne Phytophthora diseases.
The Uses of Metalaxyl
Agricultural fungicide. Phenylamide fungicide or use in food crops, shrubs and turf.
The Uses of Metalaxyl
Systemic fungicide used to control a variety of diseases on a wide range of temperate, subtropical and tropical crops.
Definition
ChEBI: Methyl N-(2,6-dimethylphenyl)-N-(methoxyacetyl)alaninate is an alanine derivative that is methyl alaninate in which one of the hydrogens attached to the nitrogen is substituted by a methoxyacetyl group, while the other is substituted by a 2,6-dimethylphenyl group. It is an alanine derivative, an aromatic amide, a carboxamide, an ether and a methyl ester.
Hazard
Moderately toxic by ingestion.
Agricultural Uses
Fungicide: Metalaxyl is used as a systemic fungicide on a variety of food and non-food crops including tobacco, turf and conifers, and ornamentals. Used in combination with fungicides of different mode of action as a foliar spray on tropical and subtropical crops; as a seed treatment to control downy mildew; and as a soil fumigant to control soilborne pathogens.
Trade name
AGROX® PREMIERE; ALLEGIENCE®; APRON®; CG 117®; CGA-48988®; CHLORAXYL®; COTGUARD®; EPERON®; DELTA-COAT; FOLIO® GOLD; GAUCHO®; KODIAK®; METALAXIL®; METAXANIN®; PACE®; PREVAIL®; RAXIL® (tebu- conazole + metalaxyl); RIDOMIL® GOLD/BRAVO®; RIDOMIL®; RIDOMIL 2E®; SUBDUE®
Pharmacology
In mycelium of Phytophthora
megasperma,metalaxyl affected primarily rRNA synthesis
(polymerase I), whereas mRNA was much less sensitive;
therefore, inhibition of rRNA synthesis is considered as
the primary site of action of PAFs (23).
The PAFs exhibit strong preventive and curative
activity. They affect especially hyphal growth (inside and
outside the plant tissue) as well as haustorium and spore
formation (15). Although not fully utilized for resistance
management reasons, PAFs also exhibit strong eradicative
and antisporulant activity in the disease cycle of target
pathogens. On the other hand, PAFs do not inhibit the
early stages in the disease cycle like zoospore release,
spore germination, and penetration of the host tissue (15).
Because spores contain many ribosomes to support early
growth stages, RNA synthesis is fully operating only
after spore germination; later development stages are
therefore most sensitive to PAFs (23). As a consequence
of RNA inhibition, the precursors of RNA synthesis (i.e.,
nucleoside triphosphates) are accumulated; they activate
β-1,3-glucansynthetases, which are involved in cell wall
formation (23). Metalaxyl-treated hyphae often produce
thicker cell walls than do untreated ones.
Safety Profile
Moderately toxic by ingestion. When heated to decomposition it emits toxic fumes of NOx.
Potential Exposure
Metalaxyl is phenylamide systemic fungicide used on a variety of food and nonfood crops including tobacco, turf and conifers, and ornamentals. Used in combination with fungicides of different mode of action as a foliar spray on tropical and subtropical crops; as a seed treatment to control downy mildew; and as a soil fumigant to control soil-borne pathogens. Banned for use in EU.
Environmental Fate
Soil. Little information is available on the degradation of metalaxyl in soil; however,
Sharom and Edgington (1986) reported metalaxyl acid as a possible metabolite. Repeated
applications of metalaxyl decreases its persistence. Following an initial application, the
average half-life was 28 days. After repeated applications, the half-life decreased to 14
days (Bailey and Coffey, 1985).
Carsel et al. (1986) studied the persistence of metalaxyl in various soil types. The
application rate was 2.2 kg/ha. In a fine sand, metalaxyl concentrations at soil depths of
15, 20, 45 and 60 cm were 100, 150, 100 and 75 ppb, respectively, 55 days after
Plant. In plants, metalaxyl undergoes ring oxidation, methyl ester hydrolysis, ether
cleavage, ring methyl hydroxylation and N-dealkylation (Owen and Donzel, 1986). Metalaxyl
acid was identified as a hydrolysis product in both sunflower leaves an
In pigeon peas, metalaxyl may persist up to 12 days (Indira et al., 1981; Chaube et
al., 1984).
Metabolic pathway
O-Demethylation is one of the major routes of metalaxyl degradation in the plant cell suspension culture. Although hydroxylation of methyl groups in the phenyl ring predominates in both lettuce and grapes, species differences are evident in grapes, whereas N-dealkylation and aryl hydroxylation are less important in lettuce. Two isomeric metabolites of methyl hydroxylation and the hydroxylated metabolite of the phenyl ring are identified as fungus metabolites. By UV irradiation of metalaxyl in aqueous solution, two rearrangement products of the N-acyl group to the 4-position on the phenyl ring are identified.
Metabolism
The degradation pathways of pesticides are published in the "FAO Plant Production and Protection Papers." Because the degradation pathways are similar for all PAF). In plants, metalaxyl is metabolized by four types of phase I reaction to form eight metabolites; at phase II, most of the metabolites are sugar-conjugated. The types of reaction in phase I are hydroxylation at the phenyl ring, oxidation of one of the tolylic methyl groups (Formula d), hydrolysis of the methyl ester (Formula e), and ether cleavage (Formula b). In phases II and III, there is also a dealkylation of the nitrogen (Formula l), in addition to the combination of the above-mentioned reaction types forming the compounds of Formulas f, h, and m. In mammals, following oral administration, metalaxyl is rapidly absorbed and rapidly and almost completely eliminated with urine and feces. Metabolism proceeds via the same degradation pathways as in plants, leading to products containing an oxidized tolylic methyl group with or without the hydrolyzed ester function (Formulas d, h, and i, respectively) containing a dealkylated nitrogen and a hydroxy group formed by ether cleavage (Formula l via b or e/f), containing an oxalyl function formed by ether cleavage followed by oxidation of the generated alcohol (Formula c), and containing the hydroxylated phenyl ring (Formula a). Residues in tissues were generally low, and there was no evidence for accumulation or retention of metalaxyl or its metabolites. In soil, similar degradation products are found as in plants and animals with the exception of three additional products of Formulas k, n, and g.
Shipping
UN3077 Environmentally hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required.
Degradation
Metalaxyl is very stable in neutral and acidic media at room temperature
and it is reasonably stable to aqueous photolysis. Its calculated
half-lives in buffers at 25 °C below pH 7 are <3 years and at pH 9, 12
weeks. Only at pH 11 was measurable hydrolysis seen (half-life 1.6
days) (Melkebeke et al., 1986). Thus environmental degradation can be
expected to be slow.
[14C-phenyl]Metalaxy1ir radiated in aqueous solution with UV light at
30 °C was degraded with a half-life of 2-3 days at four pH values between
2.8 and 8.8. Acetone (1%) accelerated the rate of decomposition. Two
rearrangement products (2 and 3) were isolated at pH 6.8; these accounted
for 3 and 6% of the radioactivity, respectively. Irradiation of 2 showed that
it was a precursor of compound 3 (Yao et al., 1989). Though these products
appear to be unusual, there is a precedent for such reactions and the
structures were determined by 1H and 13C NMR spectroscopy.
Decomposition under simulated sunlight was slower with a half-life of
297 days (Pirisi et al., 1996). Amide bond cleavage and N-dealkylation to
compounds 4 and 5 was reported. The dimethylaniline (6) was a putative
product but a separate experiment showed that it was degraded at a
higher rate than the parent and so was not observed from metalaxyl. The
products are shown in Scheme 1.
Toxicity evaluation
If used according to label recommendations, PAFs are considered to be safe to humans, animals, and the environment. The active ingredients represent only low-to-moderate acute oral and dermal hazard to rats, mice, and rabbits. The compounds do not exhibit mutagenic, oncogenic, and teratogenic hazards. No or only weak (furalaxyl, ofurace) skin irritant potential exists in rabbits and no skin sensitization is present in guinea pigs, whereas some compounds are weak to serious eye irritants in rabbits (except benalaxyl and oxadixyl). In long-term toxicity studies, the "no-observableeffect level" (NOEL) in rats is 2.5 mg/kg body weight/day for metalaxyl, metalaxyl-M, and ofurace; 5 mg/kg for benalaxyl; and 11 mg/kg for oxadixyl, whereas in dogs, the NOEL is 8.0 mg/kg body weight/day for metalaxyl and metalaxyl-M, 7 mg/kg for benalaxyl, and 12 mg/kg for oxadixyl. Using a safety factor of 100, the "acceptable daily intake" (ADI) for PAFs ranges from 0.025 to 0.11 mg/kg. The PAFs are unlikely to pose any toxicological risk to birds (bobwhite quail, mallard ducks), fish (rainbow trout, carp), honeybees, earthworms, Daphnia, and algae. The observed LD50 (LC, EC) values are very favorable for all PAFs; only benalaxyl shows lower figures in respect to earthworm, Daphnia, and algae.
Incompatibilities
Incompatible with alkaline materials, strong acids, oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Compounds of the carboxyl group react with all bases, both inorganic and organic (i.e., amines) releasing substantial heat, water and a salt that may be harmful. Incompatible with arsenic compounds (releases hydrogen cyanide gas), diazo compounds, dithiocarbamates, isocyanates, mercaptans, nitrides, and sulfides (releasing heat, toxic, and possibly flammable gases), thiosulfates and dithionites (releasing hydrogen sulfate and oxides of sulfur).
Waste Disposal
Small amounts may be destroyed by alkaline hydrolysis. Admixture with alkali can be followed by soil burial. Larger quantities can be disposed of by incineration in admixture with acetone or xylene and using effluent gas scrubbing. Do not reuse empty container; proper disposal required.
Properties of Metalaxyl
Melting point: | 72-73°C |
Boiling point: | 422.1°C (rough estimate) |
Density | 1.1083 (rough estimate) |
vapor pressure | 7.5 x 10-4 Pa (25 °C) |
refractive index | 1.5130 (estimate) |
Flash point: | 100 °C |
storage temp. | Sealed in dry,2-8°C |
solubility | Chloroform (Slightly), Methanol (Slightly) |
form | neat |
pka | 1.41±0.50(Predicted) |
form | Solid |
color | Off-White to Pale Beige |
Water Solubility | 0.84 g/100 mL |
BRN | 2947777 |
CAS DataBase Reference | 57837-19-1(CAS DataBase Reference) |
NIST Chemistry Reference | Dl-alanine, n-(2,6-dimethylphenyl)-n-(methoxyacetyl)-, methyl ester(57837-19-1) |
EPA Substance Registry System | Metalaxyl (57837-19-1) |
Safety information for Metalaxyl
Signal word | Warning |
Pictogram(s) |
Exclamation Mark Irritant GHS07 |
GHS Hazard Statements |
H302:Acute toxicity,oral H317:Sensitisation, Skin H412:Hazardous to the aquatic environment, long-term hazard |
Precautionary Statement Codes |
P261:Avoid breathing dust/fume/gas/mist/vapours/spray. P264:Wash hands thoroughly after handling. P264:Wash skin thouroughly after handling. P273:Avoid release to the environment. P280:Wear protective gloves/protective clothing/eye protection/face protection. P301+P312:IF SWALLOWED: call a POISON CENTER or doctor/physician IF you feel unwell. P302+P352:IF ON SKIN: wash with plenty of soap and water. |
Computed Descriptors for Metalaxyl
Abamectin manufacturer
Astec Lifesciences Ltd
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