White phosphorus
 White phosphorus sample with a chunk removed from the corner to expose un-oxidized material
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 Tetraphosphorus molecule
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| Names | |
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| IUPAC names
White phosphorus
Tetraphosphorus | |
| Systematic IUPAC name
1,2,3,4-Tetraphosphatricyclo[1.1.0.02,4]butane | |
Other names
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.107.967 |
PubChemCID
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| UN number | 1381 |
CompTox Dashboard(EPA)
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| Properties | |
| P4 | |
| Molar mass | 123.895g·mol−1 |
| Density | 1.82 g/cm3 |
| Melting point | 44.1 °C; 111.4 °F; 317.3 K |
| Boiling point | 280 °C; 536 °F; 553 K |
| Hazards | |
| NFPA 704(fire diamond) | |
Except where otherwise noted, data are given for materials in theirstandard state(at 25 °C [77 °F], 100 kPa).
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White phosphorus,yellow phosphorus,or simplytetraphosphorus(P4) is anallotrope of phosphorus.It is a translucentwaxysolid that quickly yellows in light (due to itsphotochemicalconversion intored phosphorus),[1]and impure white phosphorus is for this reason called yellow phosphorus. White phosphorus is the first allotrope of phosphorus, and in fact the firstelementary substanceto be discovered that was not known since ancient times.[2]It glows greenish in the dark (when exposed to oxygen) and is highlyflammableandpyrophoric(self-igniting) upon contact with air. It istoxic,causing severeliver damageon ingestion andphossy jawfrom chronic ingestion or inhalation. The odour of combustion of this form has a characteristic garlic odor, and samples are commonly coated with white "diphosphorus pentoxide",which consists ofP4O10tetrahedra with oxygen inserted between the phosphorus atoms and at their vertices. White phosphorus is only slightly soluble in water and can be stored under water.P4is soluble inbenzene,oils,carbon disulfide,anddisulfur dichloride.
Structure
[edit]
White phosphorus exists asmoleculesof four phosphorusatomsin a tetrahedral structure, joined by six phosphorus—phosphorussingle bonds.Thetetrahedralarrangement results inring strainand instability.[3]Although both are called "white phosphorus", in fact two different crystal allotropes are known, interchanging reversibly at 195.2 K.[4]The element'sstandard stateis thebody-centered cubicα form, which is actuallymetastableunderstandard conditions.[3]The β form is believed to have ahexagonalcrystal structure.[4]
Molten and gaseous white phosphorus also retains the tetrahedral molecules, until 800 °C (1,500 °F; 1,100 K) when it starts decomposing toP
2molecules.[5]TheP
4molecule in the gas phase has a P-P bond length ofrg= 2.1994(3) Å as was determined bygas electron diffraction.[6]The β form of white phosphorus contains three slightly differentP
4molecules, i.e. 18 different P-P bond lengths — between 2.1768(5) and 2.1920(5) Å. The average P-P bond length is 2.183(5) Å.[5]
Chemical properties
[edit]Despite white phosphorus not being the most stable allotropes of phosphorus, its molecular nature allows it to be easily purified. Thus, it's defined to have a zeroenthalpy of formation.
Inbase,white phosphorus spontaneouslydisproportionatestophosphineand various phosphorusoxyacidsalts.[7]
Many reactions of white phosphorus involve insertion into the P-P bonds, such as the reaction with oxygen, sulfur,phosphorus tribromideand theNO+ion.
It ignites spontaneously in air at about 50 °C (122 °F), and at much lower temperatures if finely divided (due tomelting-point depression). Phosphorus reacts with oxygen, usually formingtwooxides depending on the amount of available oxygen:P4O6(phosphorus trioxide) when reacted with a limited supply of oxygen, andP4O10when reacted with excess oxygen. On rare occasions,P4O7,P4O8,andP4O9are also formed, but in small amounts. This combustion gives phosphorus(V) oxide:
- P4+ 5 O2→ P4O10
Production and applications
[edit]The white allotrope can be produced using several methods. In the industrial process,phosphate rockis heated in an electric or fuel-firedfurnacein the presence ofcarbonandsilica.[8]Elemental phosphorus is then liberated as a vapour and can be collected underphosphoric acid.An idealized equation for thiscarbothermal reactionis shown forcalcium phosphate(although phosphate rock contains substantial amounts offluoroapatite,which would also formsilicon tetrafluoride):
- 2 Ca3(PO4)2+ 6 SiO2+ 10 C → 6 CaSiO3+ 10 CO + P4
In this way, an estimated 750,000 tons were produced in 1988.[9]
Most (83% in 1988) white phosphorus is used as a precursor to phosphoric acid, half of which is used for food or medical products where purity is important. The other half is used for detergents. Much of the remaining 17% is mainly used for the production of chlorinated compoundsphosphorus trichloride,phosphorus oxychloride,andphosphorus pentachloride:[10]
- P4+ 10Cl2→ 4PCl5
Other products derived from white phosphorus includephosphorus pentasulfideand various metal phosphides.[9]
Other polyhedrane analogues
[edit]Although white phosphorus forms thetetrahedron,the simplest possiblePlatonic hydrocarbon,no other polyhedral phosphorus clusters are known.[11]White phosphorus converts to the thermodynamically-stabler red allotrope, but that allotrope is not isolated polyhedra.
Cubane,in particular, is unlikely to form,[11]and the closest approach is the half-phosphorus compoundP4(CH)4,produced fromphosphaalkynes.[12]Other clusters are more thermodynamically favorable, and some have been partially formed as components of larger polyelemental compounds.[11]
Safety
[edit]White phosphorus is rather acutely toxic, with a lethal dose of 50-100 mg (1 mg/kg body weight). Its mode of action is thought to involve its reducing properties. It is metabolized to phosphate, which is not toxic.[9]
White phosphorus is used as a weaponbecause it is pyrophoric. For the same reasons, it is dangerous to handle. Measures are taken to protect samples from air. Anecdotal report of problems forbeachcomberswho may collect washed-up samples while unaware of their true nature.[13][14]
See also
[edit]References
[edit]- ^"White phosphorus".American Chemical Society.Retrieved2024-08-10.
- ^Weeks, Mary Elvira (1932). "The discovery of the elements. II. Elements known to the alchemists".Journal of Chemical Education.9(1): 11.Bibcode:1932JChEd...9...11W.doi:10.1021/ed009p11.
- ^abHousecroft, C. E.; Sharpe, A. G. (2004).Inorganic Chemistry(2nd ed.). Prentice Hall. p. 392.ISBN978-0-13-039913-7.
- ^abDurif, A.; Averbuch-Pouchot, M.T. (1996).Topics in phosphate chemistry.Singapore [u.a.]: World Scientific. p. 3.ISBN978-981-02-2634-3.
- ^abSimon, Arndt; Borrmann, Horst; Horakh, Jörg (1997). "On the Polymorphism of White Phosphorus".Chemische Berichte.130(9): 1235–1240.doi:10.1002/cber.19971300911.
- ^Cossairt, Brandi M.; Cummins, Christopher C.; Head, Ashley R.; Lichtenberger, Dennis L.; Berger, Raphael J. F.; Hayes, Stuart A.; Mitzel, Norbert W.; Wu, Gang (2010-06-01). "On the Molecular and Electronic Structures of AsP3 and P4".Journal of the American Chemical Society.132(24): 8459–8465.doi:10.1021/ja102580d.ISSN0002-7863.PMID20515032.
- ^Engel, Robert; Cohen, JaimeLee Iolani (2004).Synthesis of Carbon-Phosphorus Bonds(2nd ed.). Boca Raton:CRC Press.§2.3.ISBN0-8493-1617-0.LCCN2003060796.
- ^Threlfall, R.E., (1951).100 years of Phosphorus Making: 1851–1951.Oldbury:Albright and WilsonLtd
- ^abcDiskowski, Herbert; Hofmann, Thomas (2000). "Phosphorus".Ullmann's Encyclopedia of Industrial Chemistry.doi:10.1002/14356007.a19_505.ISBN978-3-527-30385-4.
- ^Chemistry Part I Class XII(PDF)(Reprinted ed.). India: NCERT. January 2019. p. 177.ISBN978-81-7450-648-1.
- ^abcCorbridge, D. E. C. (1995) "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam. § 4.1.12.ISBN0-444-89307-5.
- ^Streubel, Rainer (1995). "Phosphaalkyne Cyclooligomers: From Dimers to Hexamers—First Steps on the Way to Phosphorus–Carbon Cage Compounds".Angewandte Chemie International Edition in English.34(4): 436–438.doi:10.1002/anie.199504361.
- ^"A dangerous guide to beachcombing".
- ^"Woman mistakes WWII-era munition for precious stone on German beach | DW | 05.08.2017".Deutsche Welle.