22224-92-6

Fenamiphos is a colorless crystal or a tan, waxy solid. It is non-corrosive to metals and breaks down readily in strong acids and bases. Fenamiphos is used as a nematicide and an insecticide. It is sparingly soluble in water, but readily soluble in dichloromethane, isopropanol, and toluene. It is used primarily for the control of nematodes and thrips on citrus, grapes, peanuts, pineapples, tobacco, turf, and ornamentals. There are no residential uses for fenamiphos. The US EPA has grouped fenamiphos as an RUP owing to its high acute toxicity and toxicity to wildlife. Reports have indicated that the manufacture and sale of fenamiphos is to be phased out by 2007–2008.

Brown waxy solid or colorless solid. Used as a nematocide.

Organothiophosphates, such as FENAMIPHOS(22224-92-6), are susceptible to formation of highly toxic and flammable phosphine gas in the presence of strong reducing agents such as hydrides. Partial oxidation by oxidizing agents may result in the release of toxic phosphorus oxides.

This compound is hydrolyzed by strong acids and strong alkalis.

Toxic by inhalation and skin contact. Questionable carcinogen.

Occupational exposures to fenamiphos cause severe toxicity and adverse health effects. It inhibits the activity of the cholinesterase enzyme in humans, leading to over stimulation of the nervous system. The symptoms of poisoning include, but are not restricted to, nausea, dizziness, confusion, impaired memory, disorientation, severe depression, irritability, headache, speech diffi culties, delayed reaction times, nightmares, sleepwalking, and drowsiness or insomnia. Very high exposures, such as accidental ingestion and/or major spillage, cause respiratory paralysis and death. Laboratory studies have indicated that the teratogenic effects of fenamiphos occurred only at levels that caused overt maternal toxicity and are likely indirect consequences of this toxicity. Other studies have indicated that fenamiphos is non-mutagenic and also have no evidence suggesting that fenamiphos is carcinogenic to animals and humans.

This material is highly toxic orally, by inhalation, and by absorption through the skin. (Non-Specific--Parathion) Death may occur from respiratory failure.

(Non-Specific--Organophosphorus Pesticide, n.o.s.) Container may explode in heat of fire. Fire and runoff from fire control water may produce irritating or poisonous gases. Emits toxic fumes of nitrogen oxides, phosphorus oxides, and sulfur oxides when heated to decomposition.

Fenamiphos is primarily used to control nematodes in a wide range of crops and in turf. It will also control mites and sucking insects in crops.

Nematocide and insecticide.

Nematocide.

Systemic broad spectrum nematocide with anticholinesterase activity. Nematocide.

ChEBI: Fenamiphos is a phosphoramidate ester, an organophosphate insecticide and an organophosphate nematicide. It has a role as an EC 3.1.1.7 (acetylcholinesterase) inhibitor, an agrochemical and an acaricide. It is functionally related to a 4-(methylsulfanyl)-m-cresol.

The commercial production of fenamiphos begins with the synthesis of 3-methyl-4-(methylthio)phenol, which serves as the aromatic base. This compound is prepared by methylating a substituted phenol and introducing a methylthio group via thiolation. Separately, ethyl dichlorophosphate is reacted with isopropylamine to form ethyl isopropylphosphoramidate, a key intermediate containing the phosphorus-nitrogen bond. The final step involves a condensation reaction between the phenol derivative and the phosphoramidate in the presence of a base such as triethylamine, forming the organophosphate ester linkage that defines fenamiphos. The crude product is then purified through solvent extraction and distillation to remove impurities and unreacted materials

Notclassified

Nematicide, Insecticide: A U.S. EPA restricted Use Pesticide (RUP). Fenamiphos is an organophosphate nematicide used to control a wide variety of nematode (roundworm) pests. Nematodes can live as parasites on the outside or the inside of a plant. They may be free living or associated with cyst and root-knot formations in plants. Fenamiphos is used on a variety of plants including tobacco, turf, bananas, pineapples, citrus and other fruit vines, some vegetables, and grains. The compound is absorbed by roots and is then distributed throughout the plant. Fenamiphos, as is typical of other organophosphates, blocks the enzyme acetylcholinesterase in the target pest. The pesticide also has secondary activity against other invertebrates such as sucking insects and spider mites.

BAY 68138®; Bayer 68138®; NEMACUR®; NEMACURP®

Systemic, contact action, absorbed through roots. Acetylcholinesterase (AchE) inhibitor.

AgriculturalChemical; Reproductive Effector. Those involved in themanufacture, formulation, or application of this nematocide.

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seekmedical attention immediately. If this chemical contactsthe skin, remove contaminated clothing and wash immediately with soap and water. Speed in removing materialfrom skin is of extreme importance. Shampoo hairpromptly if contaminated. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions,including resuscitation mask) if breathing has stopped andCPR if heart action has stopped. Transfer promptly to amedical facility. When this chemical has been swallowed,get medical attention. Give large quantities of water andinduce vomiting. Do not make an unconscious personvomit.

Soil. Oxidizes in soil to the corresponding sulfone and sulfoxide (Lee et al., 1986). Fenamiphos rapidly degraded in Arredondo soil to fenamiphos sulfone and at the sametime to the corresponding phenol. The half-life in this soil is 38–67 days (Ou and Rao, 1986).
Surface Water. In estuarine water, the half-life of fenamiphos was 1.80 days (Lacorte et al., 1995).
Chemical/Physical. Emits toxic fumes of phosphorus, nitrogen and sulfur oxides when heated to decomposition (Sax and Lewis, 1987; Lewis, 1990).

Fenamiphos is an effective nematicide with both protectant and curative action. Free-living, ecto- and endo-parasitic, cyst-forming and root knot nematodes are controlled. Foliarly applied compound is translocated in plants to the roots and there is evidence that both translocation and optimum anti-cholinesterase and nematicide activity require oxidation of the thiomethyl group to the sulfoxide or the sulfone. These thiooxidation products are much more easily hydrolysed than fenamiphos itself and hydrolytic degradation in the environment most probably occurs via the formation of these intermediates.

The oxidation of the thiomethyl group to the sulfoxide and sulfone is required for both translocation and nematicidal activity in plants. The oxidation products are more susceptible to hydrolysis than fenamiphos itself. In mammals, orally administered fenamiphos is rapidly metabolized to the sulfoxide and sulfone, followed by subsequent hydrolysis, conjugation, and excretion in the urine. N-Dealkylation also occurs. The DT₅₀ in soils is several weeks; the major degradation products are fenamiphos sulfoxide and sulfone and their phenols.

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Store in tightly closed containers in a cool, well-ventilated area.

This material falls under Organophosphorus pesticides, solid, toxic, n.o.s. This compound requires a shipping label of “POISONOUS/TOXIC MATERIALS.” It fallsin Hazard Class 6.1 and Packing Group I.

For an organophosphorus compound, fenamiphos is relatively stable to hydrolysis. The DT₅₀s at pH values 4, 7 and 8 were 1 year, 8 years and 3 years respectively (PM). Fenamiphos was fairly stable in phosphate buffers at pH values 5 and 7 at 30-50 °C in the dark but in natural pond water containing silt the DT₅₀ was about 5 days. In pH 9 buffer the DT₅₀ was about 13 days. Under basic conditions the main product of hydrolysis was the phenol (2) (Waggoner and Khasawinah, 1974).
Walia and Dureja (1990) have studied the photolysis of fenamiphos in methanol solution irradiated by an unfiltered high pressure mercury lamp. The photosensitiser and singlet oxygen generator Rose Bengal was also included in one of the experiments. Analysis and characterisation were carried out by TLC, MS and ¹H NMR. In the presence of Rose Bengal the major product was fenamiphos sulfoxide (3). Since singlet oxygen is generated on soil surfaces and in silty water this experiment may be of relevance to the activation of fenamiphos in the environment. In the absence of a photosensitiser, the compound was cleaved to produce the phenol, 3-methyl-4-(methylthio)phenol (2) and its O-methylated derivative (not shown in Scheme 1), indicative of the involvement of methanol in the reaction. In an experiment which more closely mimicked the conditions for photodegradation in the environment, Barcelo et al. (1993) examined the photolysis of fenamiphos in water containing 24% methanol irradiated by a xenon arc (suntest) lamp. Metabolites were analysed and characterised by HPLC, thermospray MS and W (diode array) spectra. Fenamiphos was photodegraded to the extent of 98% after 90 min of irradiation. The main degradation product identified was fenamiphos sulfoxide (3). Products of the hydrolysis and photolysis of fenamiphos are shown in Scheme 1.

The acute oral LD₅₀ for rats is about 6 mg/kg. Inhalation LC50 (4 h) for rats is about 0.12 mg/L air. NOEL (2 yr) for rats is 1 mg/kg diet (0.05 mg/kg/d). ADI is 0.5 μg/kg b.w.

May hydrolyze under alkaline conditions.Keep away from moisture.

Nematicide