Title: Fenthion
CAS Registry Number: 55-38-9
CAS Name: Phosphorothioic acid O,O-dimethyl O-[3-methyl-4-(methylthio)phenyl] ester
Additional Names: O,O-dimethyl O-(4-methylmercapto-3-methylphenyl) thionophosphate; O,O-dimethyl O-(3-methyl-4-methylthiophenyl) thiophosphate; O,O-dimethyl O-(4-methylthio-3-methylphenyl) thiophosphate; O,O-dimethyl O-[4-(methylthio)-m-tolyl] phosphorothioate; 4-methylmercapto-3-methylphenyl dimethyl thiophosphate
Manufacturers' Codes: Bayer 29493; ENT-25540; S-1752
Trademarks: Baycid (Bayer); Baytex (Parke-Davis); Entex (obsolete); Lebaycid; Mercaptophos (Bayer); Queletox; Talodex; Tiguvon (Bayer)
Molecular Formula: C10H15O3PS2
Molecular Weight: 278.33
Percent Composition: C 43.15%, H 5.43%, O 17.25%, P 11.13%, S 23.04%
Literature References: Cholinesterase inhibitor. Prepn: Schrader, Die Entwicklung neuer insektizider Phosphorsäure-Ester (Verlag Chemie, 3rd ed., 1963) pp 298-313; Schlegk, Schrader, DE 1116656 C.A. 56, 14170g (1962); and US 3042703 (1961 and 1962, both to Bayer); Nishizawa, Mizutani, JP 64 15130 (1964 to Sumitomo), C.A. 61, 16016h (1964). Properties: Jung, Bull. WHO 21, 215 (1959); Schrader, loc. cit. Toxicity: Gaines, Toxicol. Appl. Pharmacol. 2, 88 (1960).
Properties: Liquid, slight odor of garlic. bp0.01 87°. Commercial product, bp0.01 105°. d420 1.250. nD20 1.5698. Vapor pressure at 20°: 3´10-5 mm Hg. Thermally stable up to 210°; resistant to alkalies up to pH 9. Readily sol in methanol, ethanol, ether, acetone and many other organic solvents, esp chlorinated hydrocarbons. Practically insol in water (55 mg/l). LD50 in male, female rats (mg/kg): 215, 245 orally (Gaines).
Boiling point: bp0.01 87°; bp0.01 105°
Index of refraction: nD20 1.5698
Density: d420 1.250
Toxicity data: LD50 in male, female rats (mg/kg): 215, 245 orally (Gaines)
CAUTION: Potential symptoms of overexposure are nausea, vomiting, abdominal cramps, diarrhea, salivation; headache, giddiness, vertigo, weakness; rhinorrhea, chest tightness; blurred vision, miosis; cardiac irregularities; muscle fasciculations; dyspnea. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 144.
Use: Insecticide; acaricide.
Therap-Cat-Vet: Ectoparasiticide.
Fentiazac Fenticlor Fenticonazole Fentonium Bromide Fentrazamide

Fenthion Structural Formulae .V.1.svg
CAS number 55-38-9 YesY
PubChem 3346
ChemSpider 3229 YesY
KEGG D07950 YesY
ChEBI CHEBI:34761 YesY
ATCvet code QP53BB02
Jmol-3D images Image 1
Molecular formula C10H15O3PS2
Molar mass 278.33 g/mol
Appearance colorless, almost odorless liquid; 95-98% pure fenthion is a brown oily liquid with a weak garlic odor
Density 1.250 g/cm3 (at 20 °C / 4 °C)
Melting point 7 °C; 45 °F; 280 K
Boiling point 87 °C; 189 °F; 360 K (at 0.01 mmHg)
Solubility in water 54-56 ppm (at 20 °C)
Solubility in glyceride oils, methanol, ethanol, ether, acetone, and most organic solvents, especially chlorinated hydrocarbons soluble
Vapor pressure 4 • 10-5 mmHg (at 20 °C)
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Fenthion is an organothiophosphate insecticide, avicide, and acaricide. Like most other organophosphates, its mode of action is via cholinesterase inhibition. Due to its relatively low toxicity towards humans and mammals, fenthion is listed as moderately toxic compound in U.S. Environmental Protection Agency and World Health Organization toxicity class.[2][1]