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| Names | |
|---|---|
| IUPAC name Phosphorus trichloride | |
| Systematic IUPAC name Trichlorophosphane | |
| Other names Phosphorus(III) chloride Phosphorous chloride | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChemSpider |
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| ECHA InfoCard | 100.028.864 |
| EC Number |
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| RTECS number |
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| UNII | |
| UN number | 1809 |
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| Properties | |
| PCl3 | |
| Molar mass | 137.33 g/mol |
| Appearance | Colorless to yellow fuming liquid[1] |
| Odor | unpleasant, acrid, smells likeHCl from rapidhydrolysis caused byatmosphericmoisture[1] |
| Density | 1.574 g/cm3 |
| Melting point | −93.6 °C (−136.5 °F; 179.6 K) |
| Boiling point | 76.1 °C (169.0 °F; 349.2 K) |
| hydrolyzes | |
| Solubility in other solvents | soluble[vague] inbenzene,CS2,ether,chloroform,CCl4, halogenatedorganic solvents reacts withethanol |
| Vapor pressure | 13.3 kPa |
| −63.4·10−6 cm3/mol | |
Refractive index (nD) | 1.5122 (21 °C) |
| Viscosity | 0.65 cP (0 °C) 0.438 cP (50 °C) |
| 0.97D | |
| Thermochemistry | |
Std enthalpy of formation(ΔfH⦵298) | −319.7 kJ/mol |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Highly toxic and corrosive[2] |
| GHS labelling:[4] | |
   | |
| Danger | |
| H300,H301,H314,H330,H373 | |
| P260,P273,P284,P303+P361+P353,P304+P340+P310,P305+P351+P338 | |
| NFPA 704 (fire diamond) | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 18 mg/kg (rat, oral)[3] |
LC50 (median concentration) | 104 ppm (rat, 4 hr) 50 ppm (guinea pig, 4 hr)[3] |
| NIOSH (US health exposure limits): | |
PEL (Permissible) | TWA 0.5 ppm (3 mg/m3)[1] |
REL (Recommended) | TWA 0.2 ppm (1.5 mg/m3) ST 0.5 ppm (3 mg/m3)[1] |
IDLH (Immediate danger) | 25 ppm[1] |
| Safety data sheet (SDS) | ICSC 0696 |
| Related compounds | |
Related phosphorus chlorides | Phosphorus pentachloride Phosphorus oxychloride Diphosphorus tetrachloride |
Related compounds | Phosphorus trifluoride Phosphorus tribromide Phosphorus triiodide |
| Supplementary data page | |
| Phosphorus trichloride (data page) | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Phosphorus trichloride is aninorganic compound with thechemical formula PCl3. A colorless liquid when pure, it is an importantindustrial chemical, being used for the manufacture ofphosphites and otherorganophosphorus compounds. It is toxic and reacts readily with water or air to releasehydrogen chloride fumes.
Phosphorus trichloride was first prepared in 1808 by the French chemistsJoseph Louis Gay-Lussac andLouis Jacques Thénard by heatingcalomel (Hg2Cl2) withwhite phosphorus.[5] Later during the same year, the English chemistHumphry Davy produced phosphorus trichloride by burning white phosphorus in chlorine gas.[6]
World production exceeds one-third of a milliontonnes.[7] Phosphorus trichloride is prepared industrially by the reaction ofchlorine withwhite phosphorus, using phosphorus trichloride as the solvent. In this continuous process PCl3 is removed as it is formed in order to avoid the formation of PCl5.
It has a trigonal pyramidal shape. Its31PNMR spectrum exhibits a singlet around +220 ppm with reference to a phosphoric acid standard.[citation needed]
Thephosphorus in PCl3 is often considered to have the +3oxidation state and thechlorine atoms are considered to be in the −1 oxidation state. Most of its reactivity is consistent with this description.[8]
PCl3 is a precursor to other phosphorus compounds, undergoingoxidation tophosphorus pentachloride (PCl5),thiophosphoryl chloride (PSCl3), orphosphorus oxychloride (POCl3).
PCl3 reacts vigorously withwater to formphosphorous acid (H3PO3) andhydrochloric acid:
Phosphorus trichloride is the precursor toorganophosphorus compounds. It reacts withphenol to givetriphenyl phosphite:
Alcohols such as ethanol react similarly in the presence of abase such as a tertiary amine:[9]
With one equivalent of alcohol and in the absence of base, the first product is alkoxyphosphorodichloridite:[10]
In the absence of base, however, with excess alcohol, phosphorus trichloride converts todiethylphosphite:[11][12]
Secondaryamines (R2NH) formaminophosphines. For example,bis(diethylamino)chlorophosphine, is obtained from direct reaction ofdiethylamine and PCl3.Thiols (RSH) form P(SR)3. An industrially relevant reaction of PCl3 with amines is phosphonomethylation, which employsformaldehyde:
The common herbicideglyphosate is produced this way.
The reaction of PCl3 withGrignard reagents andorganolithium reagents is a useful method for the preparation of organicphosphines with the formula R3P (sometimes called phosphanes) such astriphenylphosphine, Ph3P.
Triphenylphosphine is produced industrially by the reaction between phosphorus trichloride,chlorobenzene, and sodium:[13]
Under controlled conditions or especially with bulky R groups, similar reactions afford less substituted derivatives such aschlorodiisopropylphosphine.
Phosphorus trichloride is commonly used to convert primary and secondary alcohols to the corresponding chlorides.[14] As discussed above, the reaction of alcohols with phosphorus trichloride is sensitive to conditions. The mechanism for the ROH →RCl conversion involves the reaction of HCl with phosphite esters:
The first step proceeds with nearly ideal stereochemistry but the final step far less so owing to an SN1 pathway.
Phosphorus trichloride undergoes a variety of redox reactions:[13]
Phosphorus trichloride has a lone pair, and therefore can act as aLewis base,[15] e.g., forming a 1:1 adduct Br3B-PCl3. Metal complexes such as Ni(PCl3)4 are known, again demonstrating the ligand properties of PCl3.
This Lewis basicity is exploited in theKinnear–Perren reaction to prepare alkylphosphonyl dichlorides (RP(O)Cl2) and alkylphosphonate esters (RP(O)(OR')2). Alkylation of phosphorus trichloride is effected in the presence ofaluminium trichloride give the alkyltrichlorophosphonium salts, which are versatile intermediates:[16]
The RPCl+
3 product can then be decomposed with water to produce an alkylphosphonic dichloride RP(=O)Cl2.
PCl3, like the more popularphosphorus trifluoride, is a ligand incoordination chemistry. One example is Mo(CO)5PCl3.[17]
PCl3 is important indirectly as a precursor toPCl5,POCl3 andPSCl3, which are used in the synthesis ofherbicides,insecticides,plasticisers,oil additives, andflame retardants.
For example, oxidation of PCl3 givesPOCl3, which is used for the manufacture oftriphenyl phosphate andtricresyl phosphate, which find application asflame retardants andplasticisers forPVC.
PCl3 is the precursor totriphenylphosphine for theWittig reaction, andphosphite esters which may be used as industrial intermediates, or used in theHorner-Wadsworth-Emmons reaction, both important methods for makingalkenes. It can be used to maketrioctylphosphine oxide (TOPO), used as an extraction agent, although TOPO is usually made via the corresponding phosphine.
PCl3 is also used directly as areagent inorganic synthesis. It is used to convert primary and secondaryalcohols intoalkyl chlorides, orcarboxylic acids intoacyl chlorides, althoughthionyl chloride generally gives better yields than PCl3.[18]
Industrial production of phosphorus trichloride is controlled under theChemical Weapons Convention, where it is listed inschedule 3, as it can be used to producemustard agents.[23]
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