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chemistry is the scientific study of the synthesis and properties of organophosphorus compounds which are organic compounds containing phosphorus 1 they are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment some organophosphorus compounds are highly effective insecticides although some are extremely toxic to humans including sarin and vx nerve agents 2 phosphorus like nitrogen is in group 15 of the periodic table and thus phosphorus compounds and nitrogen compounds have many similar properties 3 4 5 the definition of organophosphorus compounds is variable which can lead to confusion in industrial and environmental chemistry an organophosphorus compound need contain only an organic substituent but need not have a direct phosphorus carbon p c bond citation needed thus a large proportion of pesticides e g malathion are often included in this class of compounds phosphorus can adopt a variety of oxidation states and it is general to classify organophosphorus compounds based on their being derivatives of phosphorus v vs phosphorus iii which are the predominant classes of compounds in a descriptive but only intermittently used nomenclature phosphorus compounds are identified by their coordination number σ and their valency λ in this system a phosphine is a σ 3 λ 3 compound organophosphorus v compounds main categories edit phosphate esters and amides edit main article organophosphate phosphate esters have the general structure p o or 3 feature p v such species are of technological importance as flame retardant agents and plasticizers lacking a p c bond these compounds are in the technical sense not organophosphorus compounds but esters of phosphoric acid many derivatives are found in nature such as phosphatidylcholine phosphate ester are synthesized by alcoholysis of phosphorus oxychloride a variety of mixed amido alkoxo derivatives are known one medically significant example being the anti cancer drug cyclophosphamide also derivatives containing the thiophosphoryl group p s include the pesticide malathion the organophosphates prepared on the largest scale are the zinc dithiophosphates as additives for motor oil several million kilograms of this coordination complex are produced annually by the reaction of phosphorus pentasulfide with alcohols 6 illustrative organophosphates and related compounds phosphatidylcholine triphenylphosphate cyclophosphamide parathion and zinc dithiophosphate phosphoryl thioates are thermodynamically much stabler than thiophosphates which can rearrange at high temperature or with a catalytic alkylant to the former 7 73 76 sp or 3 op or 2 sr in the environment all these phosphorus v compounds break down via hydrolysis to eventually afford phosphate and the organic alcohol or amine from which they are derived phosphonic and phosphinic acids and their esters edit main articles phosphonate and phosphinate phosphonates are esters of phosphonic acid and have the general formula rp o or 2 phosphonates have many technical applications a well known member being glyphosate better known as roundup with the formula ho 2 p o ch 2 nhch 2 co 2 h this derivative of glycine is one of the most widely used herbicides bisphosphonates are a class of drugs to treat osteoporosis the nerve gas agent sarin containing both c p and f p bonds is a phosphonate citation needed phosphinates feature two p c bonds with the general formula r 2 p o or a commercially significant member is the herbicide glufosinate similar to glyphosate mentioned above it has the structure ch 3 p o oh ch 2 ch 2 ch nh 2 co 2 h illustrative examples of phosphonates and phosphinates in the order shown sarin phosphonate glyphosate phosphonate fosfomycin phosphonate zoledronic acid phosphonate and glufosinate phosphinate in aqueous solution phosphonic acids ionize to give the corresponding organophosphonates the michaelis arbuzov reaction is the main method for the synthesis of these compounds for example dimethylmethylphosphonate see figure above arises from the rearrangement of trimethylphosphite which is catalyzed by methyl iodide in the horner wadsworth emmons reaction and the seyferth gilbert homologation phosphonates are used in reactions with carbonyl compounds the kabachnik fields reaction is a method for the preparation of aminophosphonates these compounds contain a very inert bond between phosphorus and carbon consequently they hydrolyze to give phosphonic and phosphinic acid derivatives but not phosphate citation needed phosphine oxides imides and chalcogenides edit main article phosphine oxides phosphine oxides designation σ 4 λ 5 have the general structure r 3 p o with formal oxidation state 5 phosphine oxides form hydrogen bonds and some are therefore soluble in water the p o bond is very polar with a dipole moment of 4 51 d for triphenylphosphine oxide citation needed compounds related to phosphine oxides include phosphine imides r 3 pnr and related chalcogenides r 3 pe where e s se te these compounds are some of the most thermally stable organophosphorus compounds in general they are less basic than the corresponding phosphine oxides which can adduce to thiophosphoryl halides 7 73 r 3 po x 3 ps r 3 p o p x 2 s x some phosphorus sulfides can undergo a reverse arbuzov rearrangement to a dialkylthiophosphinate ester 7 55 phosphorus selenides are susceptible to further alkylation on the selenium atom 8 phosphonium salts and phosphoranes edit illustrative phosphorus v compounds the phosphonium ion p ch 2 oh 4 two resonance structures for the wittig reagent ph 3 pch 2 and pentaphenylphosphorane a rare pentaorganophophorus compound compounds with the formula pr 4 x comprise the phosphonium salts these species are tetrahedral phosphorus v compounds from the commercial perspective the most important member is tetrakis hydroxy methyl phosphonium chloride p ch 2 oh 4 cl which is used as a fire retardant in textiles approximately 2 gg are produced annually of the chloride and the related sulfate 6 they are generated by the reaction of phosphine with formaldehyde in the presence of the mineral acid ph 3 hx 4 ch 2 o p ch 2 oh 4 x a variety of phosphonium salts can be prepared by alkylation and arylation of organophosphines pr 3 r x pr 3 r x phosphoranes σ 5 λ 5 are formally derived from the unknown ph 5 9 those with five organic substituents are rare although p c 6 h 5 5 is the product of p c 6 h 5 4 and phenyllithium 10 related compounds containing both halide and organic substituents on phosphorus are fairly common phosphorus ylides are unsaturated phosphoranes known as wittig reagents e g ch 2 p c 6 h 5 3 these compounds feature tetrahedral phosphorus v and are related to phosphine oxides they too are derived from phosphonium salts wittig s original preparation begins by methylating triphenylphosphine but wittig reagent synthesis proceeds to deprotonation not a second alkylation citation needed organophosphorus iii compounds main categories edit phosphites phosphonites and phosphinites edit main articles phosphite ester phosphonite and phosphinite phosphites sometimes called phosphite esters have the general structure p or 3 with oxidation state 3 such species arise from the alcoholysis of phosphorus trichloride pcl 3 3 roh p or 3 3 hcl the reaction is general thus a vast number of such species are known phosphites are employed in the perkow reaction and the michaelis arbuzov reaction they also serve as ligands in organometallic chemistry intermediate between phosphites and phosphines are phosphonites p or 2 r and phosphinite p or r 2 such species arise via alcoholysis reactions of the corresponding phosphonous and phosphinous chlorides pcl 2 r and pclr 2 respectively the latter are produced by reaction of a phosphorus trichloride with a poor metal alkyl complex e g organomercury organolead or a mixed lithium organoaluminum compound 11 phosphines edit main article organophosphine the parent compound of the phosphines is ph 3 called phosphine in the us and british commonwealth but phosphane elsewhere 12 replacement of one or more hydrogen centers by an organic substituents alkyl aryl gives ph 3 x r x an organophosphine generally referred to as phosphines citation needed from the commercial perspective the most important phosphine is triphenylphosphine several million kilograms being produced annually it is prepared from the reaction of chlorobenzene pcl 3 and sodium 6 phosphines of a more specialized nature are usually prepared by other routes 13 phosphorus halides undergo nucleophilic displacement by organometallic reagents such as grignard reagents organophosphines are nucleophiles and ligands two major applications are as reagents in the wittig reaction and as supporting phosphine ligands in homogeneous catalysis citation needed their nucleophilicity is evidenced by their reactions with alkyl halides to give phosphonium salts phosphines are nucleophilic catalysts in organic synthesis e g the rauhut currier reaction and baylis hillman reaction where the nucleophilicity or basicity of organophosphines causes trouble they can be protected as phosphine boranes phosphines are also reducing agents as illustrated in the staudinger reduction for the conversion of organic azides to amines and in the mitsunobu reaction for converting alcohols into esters in these processes the phosphine is oxidized to phosphorus v phosphines have also been found to reduce activated carbonyl groups for instance the reduction of an α keto ester to an α hydroxy ester 14 a few halophosphines are known although phosphorus strong nucleophilicity predisposes them to decomposition and dimethylphosphinyl fluoride spontaneously disproportionates to dimethylphosphine trifluoride and tetramethylbiphosphine 15 one common synthesis adds halogens to tetramethylbiphosphine disulfide 16 alternatively alkylation of phosphorus trichloride gives a halophosphonium cation which metals reduce to halophosphines phosphaalkenes and phosphaalkynes edit main articles phosphaalkene and phosphaalkyne compounds with carbon phosphorus iii multiple bonds are called phosphaalkenes r 2 c pr and phosphaalkynes rc p they are similar in structure but not in reactivity to imines r 2 c nr and nitriles rc n respectively in the compound phosphorine one carbon atom in benzene is replaced by phosphorus species of this type are relatively rare but for that reason are of interest to researchers a general method for the synthesis of phosphaalkenes is by 1 2 elimination of suitable precursors initiated thermally or by base such as dbu dabco or triethylamine thermolysis of me 2 ph generates ch 2 pme an unstable species in the condensed phase organophosphorus 0 i and ii compounds edit compounds where phosphorus exists in a formal oxidation state of less than iii are uncommon but examples are known for each class organophosphorus 0 species are debatably illustrated by the carbene adducts p nhc 2 where nhc is an n heterocyclic carbene 17 with the formulae rp n and r 2 p 2 respectively compounds of phosphorus i and ii are generated by reduction of the related organophosphorus iii chlorides citation needed 5 phpcl 2 5 mg php 5 5 mgcl 2 2 ph 2 pcl mg ph 2 p pph 2 mgcl 2 diphosphenes with the formula r 2 p 2 formally contain phosphorus phosphorus double bonds these phosphorus i species are rare but are stable provided that the organic substituents are large enough to prevent catenation bulky substituents also stabilize phosphorus radicals many mixed valence compounds are known e g the cage p 7 ch 3 3 see also edit activity based proteomics a branch of biochemistry that often relies on organophosphorus probes to interrogate enzyme activities bihar school meal poisoning incident organophosphates organophosphites organothiophosphates references edit merriam webster merriam webster s unabridged dictionary merriam webster archived from the original on 2020 05 25 retrieved 2015 12 17 lewis robert alan 1998 lewisʼ dictionary of toxicology crc lewis p 763 isbn 978 1 56670 223 2 retrieved 18 july 2013 dillon k b mathey f nixon j f 1997 phosphorus the carbon copy john wiley sons isbn 0 471 97360 2 quin l d 2000 a guide to organophosphorus chemistry john wiley sons isbn 0 471 31824 8 racke k d 1992 degradation of organophosphorus insecticides in environmental matrices pp 47 73 in chambers j e levi p e eds organophosphates chemistry fate and effects academic press san diego isbn 0121673456 1 2 3 svara jürgen weferling norbert hofmann thomas 2006 phosphorus compounds organic ullmann s encyclopedia of industrial chemistry weinheim wiley vch doi 10 1002 14356007 a19_545 pub2 isbn 978 3527306732 1 2 3 almasi lucreţia 1971 the sulfur phosphorus bond in senning alexander ed sulfur in organic and inorganic chemistry vol 1 new york marcel dekker pp 39 106 isbn 0 8247 1615 9 lccn 70 154612 paulmier claude 1986 selenium reagents and intermediates in organic synthesis oxford uk pergamon p 11 isbn 0 08 032484 3 lccn 86 17063 dasent w e 1965 nonexistent compounds new york marcel dekker pp 153 155 lccn 65 27436 wittig georg rieber martin 1949 darstellung und eigenschaften des pentaphenyl phosphors preparation and properties of pentaphenyl phosphorus justus liebigs annalen der chemie 562 3 187 192 doi 10 1002 jlac 19495620304 engel robert cohen jaimelee iolani 2004 synthesis of carbon phosphorus bonds 2 ed boca raton crc press 4 3 2 1 7 isbn 0 8493 1617 0 lccn 2003060796 iupac compendium of chemical terminology 5th ed the gold book 2025 online version 2006 phosphanes doi 10 1351 goldbook p04548 downing j h smith m b 2003 phosphorus ligands comprehensive coordination chemistry ii 2003 253 296 doi 10 1016 b0 08 043748 6 01049 5 isbn 9780080437484 cite journal cs1 maint periodical has isbn link zhang w shi m 2006 reduction of activated carbonyl groups by alkyl phosphines formation of α hydroxy esters and ketones chem commun 2006 11 1218 1220 doi 10 1039 b516467b pmid 16518496 seel f rudolph k 1968 12 march 1968 über dimethylfluorphosphin und dimethyldifluorphosphoran z anorg allg chem in german 359 333 233 244 doi 10 1002 zaac 19683630503 durig j r saunders j e 1975 25 oct 1974 spectra and structure of organophosphorus compounds xi infrared and raman spectra of ch 3 2 pcl journal of molecular structure 27 elsevier 403 416 doi 10 1016 0022 2860 75 87051 7 adapted from saunders j e august 1972 phd university of south carolina cite thesis missing or empty title help wang yuzhong xie yaoming wei pingrong king r bruce schaefer iii schleyer paul v r robinson gregory h 2008 carbene stabilized diphosphorus journal of the american chemical society 130 45 14970 1 doi 10 1021 ja807828t pmid 18937460 external links edit organophosphorus chemistry at users ox ac uk archived 2006 04 27 at the wayback machine organophosphorus chemistry at www chem wisc edu nmr predictor for organophosphorus compound chemical shifts from alan brisdon s research group v t e organophosphorus po 3 h 2 p o 3 p 2 o 5 n h 2 o op o 3 ...