{{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 431610740 | Name = Parathion | ImageFile=Methyl&Ethylparathion.png | ImageClass = skin-invert-image | ImageFile1=Ethyl-parathion-from-AHRLS-2011-3D-balls.png | ImageClass1 = bg-transparent | PIN = ''O'',''O''-Diethyl ''O''-(4-nitrophenyl) phosphorothioate | OtherNames = E605 |Section1={{Chembox Identifiers | ChEBI_Ref = {{ebicite|changed|EBI}} | ChEBI = 27928 | SMILES = S=P(Oc1ccc(cc1)[N+]([O-])=O)(OCC)OCC | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 13844817 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 61G466064D | InChI = 1/C10H14NO5PS/c1-3-14-17(18,15-4-2)16-10-7-5-9(6-8-10)11(12)13/h5-8H,3-4H2,1-2H3 | InChIKey = LCCNCVORNKJIRZ-UHFFFAOYAR | ChEMBL_Ref = {{ebicite|correct|EBI}} | ChEMBL = 261919 | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/C10H14NO5PS/c1-3-14-17(18,15-4-2)16-10-7-5-9(6-8-10)11(12)13/h5-8H,3-4H2,1-2H3 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = LCCNCVORNKJIRZ-UHFFFAOYSA-N | CASNo_Ref = {{cascite|correct|CAS}} | CASNo = 56-38-2 | KEGG_Ref = {{keggcite|correct|kegg}} | KEGG = C06604 | PubChem = 991 | RTECS = TF4550000 | EC_number = 200-271-7 | UNNumber = 3018 2783 | Beilstein = 2059093 }} |Section2={{Chembox Properties | Properties_ref = <ref name="CRC">{{RubberBible97th|pages=3–434}}</ref> | C=10 | H=14 | N=1 | O=5 | P=1 | S=1 | Appearance = Yellow liquid | Density = {{val|1.2681|u=g.cm-3}} ({{cvt|20|C|F}}) | Solubility = {{val|1.29|u=mg/100 mL}} ({{cvt|20|C|F}}) | SolubleOther = {{ubl |Very soluble in ethanol and ethyl acetate. |Soluble in acetone and diethyl ether. }} | MeltingPtC = 5.2-7.0 | BoilingPtC = 375 | BoilingPt_notes = Decomposes over {{cvt|100|C|F}} | LogP = 3.83 | VaporPressure = {{cvt|3.78e-5|mmHg|Pa}} ({{cvt|68|F|C}})<ref name="CAMEO">{{cite web |title=Chemical Datasheet - Parathion |url=https://cameochemicals.noaa.gov/chemical/1281 |website=cameochemicals.noaa.gov |publisher=National Oceanic and Atmospheric Administration {{!}} CAMEO Chemicals |access-date=14 May 2026}}</ref> | RefractIndex = 1.537 }} |Section7={{Chembox Hazards | GHS_ref = <ref name="SigmaSDS">{{cite web |title=SDS - Parathion |url=https://www.sigmaaldrich.com/US/en/sds/sial/45607?userType=undefined |version=6.16 |website=www.sigmaaldrich.com |publisher=Millipore Sigma |access-date=14 May 2026 |pages=2-3 |format=pdf |date=25 December 2025}}</ref> | GHSPictograms = {{GHS06}}{{GHS08}}{{GHS09}} | GHSSignalWord = Danger | HPhrases = {{H-phrases|300+310+330|372|410}} | PPhrases = {{P-phrases|260|262|264|270|271|273|280|284|301+310+330|302+350+310|304+340+310|314|362|391|403+233|405|501}} | NFPA-H = 4 | NFPA-F = 1 | NFPA-I = 2 | NFPA-S = | NFPA_ref = <ref name="CAMEO"/> | FlashPtC = 120 | FlashPt_ref = <ref name="SigmaSDS"/> | TLV-TWA = {{val|0.1|u=mg/m3}}<ref name="CAMEO"/> | LD50 = {{ubl |{{val|5|u=mg/kg}} (mouse, oral) |{{val|10|u=mg/kg}} (rabbit, oral) |{{val|3|u=mg/kg}} (dog, oral) |{{val|0.93|u=mg/kg}} (cat, oral) |{{val|5|u=mg/kg}} (horse, oral) |{{val|8|u=mg/kg}} (guinea pig, oral) |{{val|2|u=mg/kg}} (rat, oral)<ref name="IDLH">{{IDLH|56382|Parathion}}</ref> }} | LC50 = {{val|84|u=mg/m3}} (rat, 4 hr)<ref name="IDLH"/> | LCLo = {{ubl |{{val|50|u=mg/m3}} (rabbit, 2 hr) |{{val|14|u=mg/m3}} (guinea pig, 2 hr) |{{val|15|u=mg/m3}} (mouse)<ref name="IDLH"/> }} | PEL = TWA {{val|0.1|u=mg/m3}} [skin] | REL = TWA {{val|0.05|u=mg/m3}} [skin] | IDLH = {{val|10|u=mg/m3}} | NIOSH_id = 0479 }} }}
'''Parathion''', also called '''parathion-ethyl''' or '''diethyl parathion''', is an organophosphate insecticide and acaricide. It was originally developed by IG Farben in the 1940s. It is highly toxic to non-target organisms, including humans, so its use has been banned or restricted in most countries. In response to safety concerns, the less toxic but still dangerous analogue parathion methyl was later developed.<ref name="Parathion and methyl parathion toxicity">{{cite journal |last1=Mirer |first1=Franklin E. |last2=Levine |first2=Barry S. |last3=Murphy |first3=Sheldon D. |title=Parathion and methyl parathion toxicity and metabolism in piperonyl butoxide and diethyl maleate pretreated mice |journal=Chemico-Biological Interactions |date=10 January 1977 |volume=17 |issue=1 |pages=99–112 |doi=10.1016/0009-2797(77)90075-8 |pmid=872271 |bibcode=1977CBI....17...99M}}</ref>
==History== thumb|Bottle with E605 Parathion was developed by Gerhard Schrader for the German trust IG Farben in the 1940s. After World War II and the collapse of IG Farben due to the war crime trials, the Western allies seized the patent, and parathion was marketed worldwide by different companies and under different brand names. The most common German brand was '''E605''' (banned in Germany after 2002); this was not a food-additive "E number" as used in the EU today. "E" stands for ''Entwicklungsnummer'' (German for "development number"). It is an irreversible acetylcholinesterase inhibitor.
In the EU, Parathion was banned in 2001.<ref>{{cite EU directive |serial=2001/520/EEC |date=9 July 2001 |description=Concerning the non-inclusion of parathion in AnnexI to Council Directive 91/414/EEC and the withdrawal of authorisations for plant protection products containing this active substance |eurlextag=32001D0520 }}</ref>
==Handling properties== It is commonly distributed as a brown liquid that smells of rotting eggs or garlic.{{cn|reason=Needs a ref (and I'd describe the smell as "like death", personally... not like dead things, but like what you'd expect dying to smell like if it smelled like something. Open a bottle of malathion concentrate for the same experience without nearly the danger.)|date=May 2026}} The insecticide is somewhat stable, although it darkens when exposed to sunlight.{{cn|date=May 2026}}
==Industrial synthesis== Parathion is synthesized from diethyl dithiophosphoric acid {{chem2|(C2H5O)2PS2H}} by chlorination to generate diethylthiophosphoryl chloride ({{chem2|(C2H5O)2P(S)Cl}}), and then the chloride is treated with sodium 4-nitrophenolate (the sodium salt of 4-nitrophenol).<ref name = fee>{{Kirk-Othmer |last1=Fee |first1=D. C. |last2=Gard |first2=D. R. |last3=Yang |first3=C. |title=Phosphorus Compounds |doi=10.1002/0471238961.16081519060505.a01.pub2 |year=2005}}</ref>
:{{chem2|2 (C2H5O)2P(S)SH + 3 Cl2 → 2 (C2H5O)2P(S)Cl + S2Cl2 + 2 HCl}} :{{chem2|(C2H5O)2P(S)Cl + NaOC6H4NO2 → (C2H5O)2P(S)OC6H4NO2 + NaCl}}
==Applications== As a pesticide, parathion is generally applied by spraying. It is often applied to cotton, rice and fruit trees. The usual concentrations of ready-to-use solutions are 0.05 to 0.1%. The chemical is banned for use on many food crops.{{cn|date=May 2026}}
==Insecticidal activity== Parathion acts on the enzyme acetylcholinesterase indirectly. After an insect (or a human) ingests parathion, an oxidase replaces the double bonded sulfur with oxygen to give paraoxon.<ref name = metcalf>{{Ullmann |last=Metcalf |first=R. L. |title=Insect Control |year=2002 |doi=10.1002/14356007.a14_263}}</ref>
:{{chem2|(C2H5O)2P(S)OC6H4NO2 + }}{{sfrac|1|2}}{{chem2| O2 -> (C2H5O)2P(O)OC6H4NO2 + S}}
The phosphate ester is more reactive in organisms than the phosphorothiolate ester, as the phosphorus atoms become much more electropositive.<ref name = metcalf/>
Parathion {{visible anchor|Resistance|text=resistance}} is a special case of acetylcholinesterase inhibitor resistance.{{cn|reason=Why is it special?|date=May 2026}}
Parathion is toxic to most forms of wildlife in addition to insects if not applied at correct concentrations.<ref name = extoxnet/>
==Degradation== Degradation of parathion leads to more water-soluble products. Hydrolysis, which deactivates the molecule, occurs at the aryl ester bond resulting in diethyl thiophosphate and 4-nitrophenol:<ref name = metcalf/>
:{{chem2|(C2H5O)2P(S)OC6H4NO2 + H2O -> HOC6H4NO2 + (C2H5O)2P(O)SH}}
Degradation proceeds differently under anaerobic conditions: the nitro group on parathion is reduced to the amine:<ref name = metcalf/>
:{{chem2|(C2H5O)2P(S)OC6H4NO2 + 6 H -> (C2H5O)2P(S)OC6H4NH2 + 2 H2O}}
==Illicit uses== ===As a chemical weapon=== Parathion was used as a chemical warfare agent, most notably by an element of the British South Africa Police attached to the Selous Scouts during the Rhodesian Bush War. They used it to poison clothing that was then supplied to anti-government guerrillas. When the enemy soldiers put on the clothes, they were poisoned by absorption through the skin.<ref>{{Cite web|url=https://openaccess.leidenuniv.nl/bitstream/handle/1887/68698/Poison%20in%20Rhodesia%2C%20Colm%20Wittenberg.pdf?sequence=1|title = Poison in Rhodesia|date = 31 January 2019}}</ref><ref>{{cite book|title=Dirty War: Rhodesia and Chemical Biological Warfare, 1975–1980|last=Cross|first=Glenn|year=2017|location=Solihull, UK|publisher=Helion & Company|isbn=978-1-911512-12-7}}</ref>
=== Use in suicides === Parathion was commonly used for suicides in the 1950s and 1960s.<ref name=":0">{{Cite book |last=Carson |first=Rachel |title=Silent Spring |publisher= HarperCollins|orig-date=1962 |isbn=978-0-547-52762-8 |oclc=1346358856}}</ref>
==Safety== Parathion disrupts the nervous system by inhibiting acetylcholinesterase. It is absorbed via skin, mucous membranes, and orally. Absorbed parathion is rapidly metabolized to paraoxon. Exposure can result in headaches, convulsions, poor vision, vomiting, abdominal pain, severe diarrhea, unconsciousness, tremor, dyspnea, and finally pulmonary edema as well as respiratory arrest. Symptoms of poisoning are known to last for extended periods, sometimes months. The most common and very specific antidote is atropine, in doses of up to {{val|100|u=mg}} daily. Because atropine may also be toxic, it is recommended that small frequently repeated doses be used in treatment. If human poisoning is detected early and the treatment is prompt (atropine and artificial respiration), fatalities are infrequent. Insufficient oxygen will lead to cerebral hypoxia and permanent brain damage. Peripheral neuropathy including paralysis is noticed as late sequelae after recovery from acute intoxication.{{cn|date=May 2026}}
Based on animal studies, parathion is considered by the U.S. Environmental Protection Agency to be a possible human carcinogen.<ref name=epa>{{cite web | title = Parathion | work = Integrated Risk Information System | publisher = U. S. Environmental Protection Agency | date = 26 January 2007 | url = http://www.epa.gov/iris/subst/0327.htm| archive-url = https://web.archive.org/web/20000823045118/http://www.epa.gov/iris/subst/0327.htm| url-status = dead| archive-date = August 23, 2000}}</ref> Studies show that parathion is toxic to fetuses, but does not cause birth defects.<ref name = extoxnet>{{cite web | work = Extension Toxicology Network | title = Pesticide Information Profiles - Parathion | publisher = Oregon State University |date=September 1993 | url = http://extoxnet.orst.edu/pips/parathio.htm}}</ref>
It is classified by the United Nations Environment Programme as a persistent organic pollutant<ref name="POP">{{cite book |last1=Sah |first1=Ram Charitra |last2=Joshi |first2=Keshab Raj |title=Fact Sheet of 22 Persistent Organic Pollutants under Stockholm Convention |date=2011 |publisher=Center for Public Health and Environmental Development (CEPHED) |location=Lalitpur, Nepal |isbn=978-9937-8479-1-9 |pages=19, 20, 53, 101 |url=https://www.undp.org/sites/g/files/zskgke326/files/2024-06/factsheet.pdf |access-date=15 August 2025 }}</ref> and by the World Health Organization as Toxicity Class Ia (extremely hazardous).<ref name="WHO">{{cite book |last1=Besil |first1=Natalia |last2=Rezende |first2=Sofia |title=Encyclopedia of Toxicology |chapter=Parathion |editor1-last=Wexler |editor1-first=Philip |date=2024 |volume=7 |edition=Fourth |pages=283–287 |doi=10.1016/B978-0-12-824315-2.00888-5 |isbn=9780123864550 |publisher=Elsevier }}</ref>
==See also== * Pesticide toxicity to bees * Parathion methyl
==References== {{reflist}}
==External links== * {{PPDB|506}} * [http://www.atsdr.cdc.gov/risk/methyl_parathion/ ATSDR - Methyl Parathion Expert Panel Report] {{Webarchive|url=https://web.archive.org/web/20190614154737/http://www.atsdr.cdc.gov/risk/methyl_parathion/ |date=2019-06-14 }} U.S. Department of Health and Human Services (public domain) * [https://www.cdc.gov/niosh/npg/npgd0479.html CDC - NIOSH Pocket Guide to Chemical Hazards] U.S. Department of Health and Human Services (public domain) * Ethyl parathion: {{ICSC|0006}} * Methyl parathion: {{ICSC|0626}}
{{Insecticides}} {{Acetylcholine metabolism and transport modulators}} {{Authority control}}
Category:Obsolete pesticides Category:Organophosphate insecticides Category:Acetylcholinesterase inhibitors Category:Neurotoxins Category:Organothiophosphate esters Category:4-Nitrophenyl compounds Category:IARC Group 2B carcinogens Category:Phenol esters Category:Ethyl esters