Phosphorus Pentachloride - Wikipedia

"PCl5" redirects here. For the printer protocol, see Printer Command Language. Phosphorus pentachloride

Names
IUPAC names Phosphorus pentachloride Pentachloro-λ5-phosphane
Other names Pentachlorophosphorane
Identifiers
CAS Number	10026-13-8 Y
3D model (JSmol)	Interactive image
ChemSpider	23204 N
ECHA InfoCard	100.030.043
EC Number	233-060-3
PubChem CID	24819
RTECS number	TB6125000
UNII	0EX753TYDU
UN number	1806
CompTox Dashboard (EPA)	DTXSID9033896
InChI InChI=1S/Cl5P/c1-6(2,3,4)5 NKey: UHZYTMXLRWXGPK-UHFFFAOYSA-N N InChI=1/Cl5P/c1-6(2,3,4)5Key: UHZYTMXLRWXGPK-UHFFFAOYAP
SMILES ClP(Cl)(Cl)(Cl)Cl
Properties
Chemical formula	Cl5P
Molar mass	208.22 g·mol−1
Appearance	yellowish white crystals
Odor	pungent, unpleasant[1]
Density	2.1 g/cm3
Melting point	160.5 °C (320.9 °F; 433.6 K)
Boiling point	166.8 °C (332.2 °F; 439.9 K) sublimation
Solubility in water	reacts
Solubility	soluble in CS2, chlorocarbons, benzene
Vapor pressure	1.11 kPa (80 °C) 4.58 kPa (100 °C)[2]
Structure
Crystal structure	tetragonal
Coordination geometry	D3h (trigonal bipyramidal)
Dipole moment	0 D
Thermochemistry
Heat capacity (C)	111.5 J/mol·K[2]
Std molarentropy (S⦵298)	364.2 J/mol·K[2]
Hazards
GHS labelling:
Pictograms	[3]
Signal word	Danger
Hazard statements	H302, H314, H330, H373[3]
Precautionary statements	P260, P280, P284, P305+P351+P338, P310[3]
NFPA 704 (fire diamond)	3 0 2W
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)	660 mg/kg (rat, oral)[4]
LC50 (median concentration)	205 mg/m3 (rat)[4]
LCLo (lowest published)	1020 mg/m3 (mouse, 10 min)[4]
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 1 mg/m3[1]
REL (Recommended)	TWA 1 mg/m3[1]
IDLH (Immediate danger)	70 mg/m3[1]
Safety data sheet (SDS)	ICSC 0544
Related compounds
Related phosphorus pentahalides	Phosphorus pentafluoridePhosphorus pentabromidePhosphorus pentaiodide
Related compounds	Phosphorus trichloridePhosphoryl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Chemical compound

Phosphorus pentachloride is the chemical compound with the formula PCl5. It is one of the most important phosphorus chlorides/oxychlorides, others being PCl3 and POCl3. PCl5 finds use as a chlorinating reagent. It is a colourless, water-sensitive solid, although commercial samples can be yellowish and contaminated with hydrogen chloride.

Structure

[edit]

The structures for the phosphorus chlorides are invariably consistent with VSEPR theory. The structure of PCl5 depends on its environment. Gaseous and molten PCl5 is a neutral molecule with trigonal bipyramidal geometry and (D3h) symmetry. The hypervalent nature of this species (as well as of PCl−6, see below) can be explained with the inclusion of non-bonding molecular orbitals (molecular orbital theory) or resonance (valence bond theory). This trigonal bipyramidal structure persists in nonpolar solvents, such as CS2 and CCl4.[5] In the solid state PCl5 is an ionic compound called tetrachlorophosphonium hexachlorophosphate formulated PCl+4PCl−6.[6]

In solutions of polar solvents, PCl5 undergoes self-ionization.[8] Dilute solutions dissociate according to the following equilibrium:

PCl5 ⇌ PCl+4 + Cl−

At higher concentrations, a second equilibrium becomes more prevalent:

2 PCl5 ⇌ PCl+4 + PCl−6

The cation PCl+4 and the anion PCl−6 are tetrahedral and octahedral, respectively. At one time, PCl5 in solution was thought to form a dimeric structure, P2Cl10, but this suggestion is not supported by Raman spectroscopic measurements.

Related pentachlorides

[edit]

AsCl5 and SbCl5 also adopt trigonal bipyramidal structures. The relevant bond distances are 211 pm (As−Cleq), 221 pm (As−Clax), 227 pm (Sb−Cleq), and 233.3 pm (Sb−Clax).[9] At low temperatures, SbCl5 converts to the dimer, dioctahedral Sb2Cl10, structurally related to niobium pentachloride.

Preparation

[edit]

PCl5 is prepared by the chlorination of PCl3.[10] This reaction is used to produce around 10,000 tonnes of PCl5 per year (as of 2000).[6]

PCl3 + Cl2 ⇌ PCl5   (ΔH = −124 kJ/mol)

PCl5 exists in equilibrium with PCl3 and chlorine, and at 180 °C the degree of dissociation is about 40%.[6] Because of this equilibrium, samples of PCl5 often contain chlorine, which imparts a greenish coloration.

Reactions

[edit]

Hydrolysis

[edit]

In its most characteristic reaction, PCl5 reacts upon contact with water to release hydrogen chloride and give phosphorus oxides. The first hydrolysis product is phosphorus oxychloride:

PCl5 + H2O → POCl3 + 2 HCl

In hot water, hydrolysis proceeds completely to orthophosphoric acid:

PCl5 + 4 H2O → H3PO4 + 5 HCl

Lewis acidity

[edit]

Phosphorus pentachloride is a Lewis acid. This property underpins many of its characteristic reactions, autoionization, chlorinations, hydrolysis. A well studied adduct is PCl5(pyridine).[11]

Chlorination of organic compounds

[edit]

In synthetic chemistry, two classes of chlorination are usually of interest: oxidative chlorinations and substitutive chlorinations. Oxidative chlorinations entail the transfer of Cl2 from the reagent to the substrate. Substitutive chlorinations entail replacement of O or OH groups with chloride. PCl5 can be used for both processes.

Upon treatment with PCl5, carboxylic acids convert to the corresponding acyl chloride.[12] The following mechanism has been proposed:[13]

It also converts alcohols to alkyl chlorides. Thionyl chloride is more commonly used in the laboratory because the resultant sulfur dioxide is more easily separated from the organic products than is POCl3.

PCl5 reacts with a tertiary amides, such as dimethylformamide (DMF), to give dimethylchloromethyleneammonium chloride, which is called the Vilsmeier reagent, [(CH3)2N=CClH]Cl. More typically, a related salt is generated from the reaction of DMF and POCl3. Such reagents are useful in the preparation of derivatives of benzaldehyde by formylation and for the conversion of C−OH groups into C−Cl groups.[14]

It is especially renowned for the conversion of C=O groups to CCl2 groups.[15] For example, benzophenone and phosphorus pentachloride react to give the diphenyldichloromethane:[16]

(C6H5)2CO + PCl5 → (C6H5)2CCl2 + POCl3

The electrophilic character of PCl5 is highlighted by its reaction with styrene to give, after hydrolysis, phosphonic acid derivatives.[17]

Comparison with related reagents

[edit]

Both PCl3 and PCl5 convert R3COH groups to the chloride R3CCl. The pentachloride is however a source of chlorine in many reactions. It chlorinates allylic and benzylic CH bonds. PCl5 bears a greater resemblance to SO2Cl2, also a source of Cl2. For oxidative chlorinations on the laboratory scale, sulfuryl chloride is often preferred over PCl5 since the gaseous SO2 by-product is readily separated.

Chlorination of inorganic compounds

[edit]

As for the reactions with organic compounds, the use of PCl5 has been superseded by SO2Cl2. The reaction of phosphorus pentoxide and PCl5 produces POCl3 :[18][page needed]

6 PCl5 + P4O10 → 10 POCl3

PCl5 chlorinates nitrogen dioxide to form unstable nitryl chloride:

PCl5 + 2 NO2 → PCl3 + 2 NO2Cl 2 NO2Cl → 2 NO2 + Cl2

PCl5 is a precursor for lithium hexafluorophosphate, LiPF6. Lithium hexafluorophosphate is a commonly employed salt in electrolytes in lithium ion batteries.[19] LiPF6 is produced by the reaction of PCl5 with lithium fluoride, with lithium chloride as a side product:

PCl5 + 6 LiF → LiPF6 + 5 LiCl

Safety

[edit]

PCl5 is a dangerous substance as it reacts violently with water. It is also corrosive when in contact with skin and can be fatal when inhaled.

History

[edit]

Phosphorus pentachloride was first prepared in 1808 by the English chemist Humphry Davy.[20] Davy's analysis of phosphorus pentachloride was inaccurate;[21] the first accurate analysis was provided in 1816 by the French chemist Pierre Louis Dulong.[22]

See also

[edit]

• Phosphorus halides
• Phosphorus trichloride
• Phosphoryl chloride
• Phosphorus trifluorodichloride

References

[edit]

1. ^ a b c d NIOSH Pocket Guide to Chemical Hazards. "#0509". National Institute for Occupational Safety and Health (NIOSH).
2. ^ a b c Phosphorus pentachloride in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD) (retrieved 2014-05-15)
3. ^ a b c Phosphorus pentachloride
4. ^ a b c "Phosphorus pentachloride". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
5. ^ Corbridge, D. E. C. (1995). Phosphorus: An outline of its chemistry, biochemistry, and uses. Elsevier Science. ISBN 0-444-89307-5.
6. ^ a b c Holleman, A. F.; Wiber, E.; Wiberg, N. (2001). Inorganic Chemistry. Academic Press. ISBN 978-0-12-352651-9.
7. ^ Finch, A.; Fitch, A.N.; Gates, P.N. (1993). "Crystal and Molecular structure of a metastable modification of phosphorus pentachloride". Journal of the Chemical Society, Chemical Communications (11): 957–958. doi:10.1039/C39930000957.
8. ^ Suter, R. W.; Knachel, H. C.; Petro, V. P.; Howatson, J. H. & Shore, S. G. (1978). "Nature of Phosphorus(V) Chloride in Ionizing and Nonionizing Solvents". Journal of the American Chemical Society. 95 (5): 1474–1479. doi:10.1021/ja00786a021.
9. ^ Haupt, S.; Seppelt, K. (2002). "Solid State Structures of AsCl5 and SbCl5". Zeitschrift für anorganische und allgemeine Chemie. 628 (4): 729–734. doi:10.1002/1521-3749(200205)628:4<729::AID-ZAAC729>3.0.CO;2-E.
10. ^ Maxson, R. N. (1939). "Phosphorus Pentachloride". Inorganic Syntheses. Vol. 1. pp. 99–100. doi:10.1002/9780470132326.ch34. ISBN 9780470132326.
11. ^ Wong, Chih Y.; Kennepohl, Dietmar K.; Cavell, Ronald G. (1996). "Neutral Six-Coordinate Phosphorus". Chemical Reviews. 96 (6): 1917–1952. doi:10.1021/cr9410880. PMID 11848816.
12. ^ Adams, R.; Jenkins, R. L. (1941). "p-Nitrobenzoyl chloride". Organic Syntheses; Collected Volumes, vol. 1, p. 394.
13. ^ Clayden, Jonathan (2005). Organic chemistry (Reprinted ed.). Oxford: Oxford University Press. ISBN 978-0-19-850346-0.
14. ^ Burks Jr., J. E. (2004). "Phosphorus(V) chloride". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York, NY: J. Wiley & Sons. doi:10.1002/047084289X.rp158. ISBN 0471936235.
15. ^ Gross, H.; Rieche, A.; Höft, E.; Beyer, E. (1973). "Dichloromethyl methyl ether". Organic Syntheses; Collected Volumes, vol. 5, p. 365.
16. ^ Spaggiari, A.; Vaccari, D.; Davoli, P.; Torre, G.; Prati, F. (2007). "A Mild Synthesis of Vinyl Halides and gem-Dihalides Using Triphenyl Phosphite−Halogen-Based Reagents". The Journal of Organic Chemistry. 72 (6): 2216–2219. doi:10.1021/jo061346g. ISSN 0022-3263. PMID 17295542.
17. ^ Schmutzler, R. (1973). "Styrylphosphonic dichloride". Organic Syntheses; Collected Volumes, vol. 5, p. 1005.
18. ^ Cotton, Frank Albert (1999). Advanced Inorganic Chemistry. Wiley-Interscience. ISBN 978-0-471-19957-1.
19. ^ Bushkova, O. V.; Yaroslavtseva, T. V.; Dobrovolsky, Yu. A. (4 August 2017). "New lithium salts in electrolytes for lithium-ion batteries (Review)". Russian Journal of Electrochemistry. 53 (7): 677–699. doi:10.1134/S1023193517070035. S2CID 103854243.
20. ^ Davy, Humphry (1809). "The Bakerian Lecture. An account of some new analytical researches on the nature of certain bodies, particularly the alkalies, phosphorus, sulphur, carbonaceous matter, and the acids hitherto undecomposed; with some general observations on chemical theory". Philosophical Transactions of the Royal Society of London. 99: 39–104. doi:10.1098/rstl.1809.0005. S2CID 98814859. On pp. 94–95, Davy mentioned that when he burned phosphorus in chlorine gas ("oxymuriatic acid gas"), he obtained a clear liquid (phosphorus trichloride) and a white solid (phosphorus pentachloride).
21. ^ Davy, Humphry (1810). "Researches on the oxymuriatic acid [i.e., chlorine], its nature and combinations; and on the elements of the muriatic acid [i.e., hydrogen chloride]. With some experiments on sulphur and phosphorus, made in the laboratory of the Royal Institution". Philosophical Transactions of the Royal Society of London. 100: 231–257. doi:10.1098/rstl.1810.0016. S2CID 95219058. On p. 257, Davy presented his empirical formula for phosphorus pentachloride: 1 portion of phosphorus to 3 portions of "oxymuriatic gas" (chlorine).
22. ^ Dulong (1816). "Extrait d'un mémoire sur les combinaisons du phosphore avec l'oxigène" [Extract from a memoir on the compounds of phosphorus with oxygen]. Annales de Chimie et de Physique. 2nd series (in French). 2: 141–150. On p. 148, Dulong presented the correct analysis of phosphorus pentachloride (which is 14.9% phosphorus and 85.1% chlorine by weight, vs. Dulong's values of 15.4% and 84.6%, respectively).

External links

[edit] Wikimedia Commons has media related to Phosphorus pentachloride.

• The period 3 chlorides
• International Chemical Safety Card 0544
• CDC - NIOSH Pocket Guide to Chemical Hazards

v t e Phosphorus compounds
Phosphides	AlP AsP BP BiP Cs2P5 Ca3P2 Cd3P2 Cu3P DyP ErP EuP GdP AuP FeP Fe3P HfP HoP InP LaP Li3P LuP MoP MoP2 Mo3P NbP NdP NpP Np3P4 OsP2 Ru2P PtP2 PrP PrP5 PuP ScP SmP SmP5 Sr3P2 TbP SnP3 ThP7 TmP YP YbP ZnP2 Zn3P2 ZrP ZrP2
Other compounds	PBr3 PBr5 PBr7 PCl3 PCl5 P2Cl4 PF3 PF5 PI3 PH3 PN P3N5 PO P2O3 P2O4 P2O5 P4S3 P4Sx P4S10

v t e Salts and covalent derivatives of the chloride ion

HCl He LiCl BeCl2 B4Cl4B12Cl12BCl3B2Cl4+BO3 C2Cl2C2Cl4C2Cl6CCl4+C+CO3 NCl3ClN3+N+NO3 ClxOyCl2OCl2O2ClOClO2Cl2O4Cl2O6Cl2O7ClO4+O ClFClF3ClF5 Ne NaCl MgCl2 AlClAlCl3 Si5Cl12Si2Cl6SiCl4 P2Cl4PCl3PCl5+P S2Cl2SCl2SCl4+SO4 Cl2 Ar KCl CaClCaCl2 ScCl3 TiCl2TiCl3TiCl4 VCl2VCl3VCl4VCl5 CrCl2CrCl3CrCl4 MnCl2MnCl3 FeCl2FeCl3 CoCl2CoCl3 NiCl2 CuClCuCl2 ZnCl2 GaClGaCl3 GeCl2GeCl4 AsCl3AsCl5+As Se2Cl2SeCl2SeCl4 BrCl Kr RbCl SrCl2 YCl3 ZrCl2ZrCl3ZrCl4 NbCl3NbCl4NbCl5 MoCl2MoCl3MoCl4MoCl5MoCl6 TcCl3TcCl4 RuCl2RuCl3RuCl4 RhCl3 PdCl2 AgCl CdCl2 InClInCl2InCl3 SnCl2SnCl4 SbCl3SbCl5 Te3Cl2TeCl2TeCl4 IClICl3 XeClXeCl2XeCl4 CsCl BaCl2 * LuCl3 HfCl4 TaCl3TaCl4TaCl5 WCl2WCl3WCl4WCl5WCl6 ReCl3ReCl4ReCl5ReCl6 OsCl2OsCl3OsCl4OsCl5 IrCl2IrCl3IrCl4 PtCl2PtCl4 AuCl(Au[AuCl4])2AuCl3 Hg2Cl2HgCl2 TlClTlCl3 PbCl2PbCl4 BiCl3 PoCl2PoCl4 AtCl Rn FrCl RaCl2 ** LrCl3 RfCl4 DbCl5 SgO2Cl2 BhO3Cl Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og   * LaCl3 CeCl3 PrCl3 NdCl2NdCl3 PmCl3 SmCl2SmCl3 EuCl2EuCl3 GdCl3 TbCl3 DyCl2DyCl3 HoCl3 ErCl3 TmCl2TmCl3 YbCl2YbCl3 ** AcCl3 ThCl3ThCl4 PaCl4PaCl5 UCl3UCl4UCl5UCl6 NpCl3 PuCl3 AmCl2AmCl3 CmCl3 BkCl3 CfCl3CfCl2 EsCl2EsCl3 FmCl2 MdCl2 NoCl2

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