White phosphorus

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This article is about the chemistry of white phosphorus. For military applications, see White phosphorus munition.
White phosphorus
White phosphorus sample with a chunk removed from the corner to expose un-oxidized material
Tetraphosphorus molecule
Names
IUPAC names
White phosphorus
tetrahedro-Tetraphosphorus
Systematic IUPAC name
1,2,3,4-Tetraphosphatricyclo[1.1.0.02,4]butane
Other names
  • Molecular phosphorus
  • Yellow phosphorus
Identifiers
3D model (
JSmol
)
ChEBI
ChemSpider
ECHA InfoCard
 100.107.967 Edit this at Wikidata
1856
UN number 1381
  • InChI=1S/P4/c1-2-3(1)4(1)2
    Key: OBSZRRSYVTXPNB-UHFFFAOYSA-N
SMILES
  • P12P3P1P23
Properties
P4
Molar mass 123.895 g·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[1]
GHS labelling:
GHS02: Flammable GHS05: Corrosive GHS06: Toxic GHS09: Environmental hazard
Danger
H250, H300+H330, H314, H400
P210, P222, P260, P264, P270, P271, P273, P280, P284, P301+P310+P330, P301+P330+P331, P303+P361+P353, P304+P340+P310, P305+P351+P338+P310, P335+P334, P363, P370+P378, P391, P403+P233, P405, P422, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no code
4
4
2
0.1 mg/m3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

White phosphorus, yellow phosphorus, or simply tetraphosphorus (P4) is an

oils, carbon disulfide, and disulfur dichloride
.

Structure

White phosphorus crystal structure

White phosphorus exists as

hexagonal crystal structure.[5]

Molten and gaseous white phosphorus also retains the tetrahedral molecules, until 800 °C (1,500 °F; 1,100 K) when it starts decomposing to P
2 molecules.[6] The P
4 molecule in the gas phase has a P-P bond length of rg = 2.1994(3) Å as was determined by gas electron diffraction.[7] The β form of white phosphorus contains three slightly different P
4 molecules, 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.[6]

Chemical properties

Despite white phosphorus not being the most stable allotropes of phosphorus, its molecular nature allows it to be easily purified. Thus, it is defined to have a zero enthalpy of formation.

In

base, white phosphorus spontaneously disproportionates to phosphine and various phosphorus oxyacid salts.[8]

Many reactions of white phosphorus involve insertion into the P-P bonds, such as the reaction with oxygen, sulfur, phosphorus tribromide and the NO+ ion.

It ignites spontaneously in air at about 50 °C (122 °F), and at much lower temperatures if finely divided (due to melting-point depression). Phosphorus reacts with oxygen, usually forming two oxides depending on the amount of available oxygen: P4O6 (phosphorus trioxide) when reacted with a limited supply of oxygen, and P4O10 when reacted with excess oxygen. On rare occasions, P4O7, P4O8, and P4O9 are also formed, but in small amounts. This combustion gives phosphorus(V) oxide:

P4 + 5 O2 → P4O10

Production and applications

The white allotrope can be produced using several methods. In the industrial process,

fluoroapatite, which would also form silicon 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.[10]

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.[

phosphorus oxychloride, and phosphorus pentachloride:[11]

P4 + 10Cl2 → 4PCl5

Other products derived from white phosphorus include phosphorus pentasulfide and various metal phosphides.[10]

Other polyhedrane analogues

Although white phosphorus forms the tetrahedron, the simplest possible Platonic solid, no other polyhedral phosphorus clusters are known.[12] White phosphorus converts to the thermodynamically-stabler red allotrope, but that allotrope is not isolated polyhedra.

A cubane-type cluster, in particular, is unlikely to form,[12] and the closest approach is the half-phosphorus compound P4(CH)4, produced from phosphaalkynes.[13] Other clusters are more thermodynamically favorable, and some have been partially formed as components of larger polyelemental compounds.[12]

Safety

White phosphorus is acutely toxic, with a lethal dose of 50-100 mg (1 mg/kg body weight). Its mode of action is not known but is thought to involve its reducing properties, possibly forming intermediate reducing compounds such as hypophosphite, phosphite, and phosphine. It damages the liver, kidneys, and other organs before eventually being metabolized to non-toxic phosphate. Chronic low-level exposure leads to tooth loss and phossy jaw which appears to be caused by the formation of amino bisphosphonates.[10][14][15]

White phosphorus is used as a weapon because it is pyrophoric. For the same reasons, it is dangerous to handle. Measures are taken to protect samples from air since it will react with oxygen at ambient temperatures, and even in small samples this can lead to self-heating and eventual combustion. There are anecdotal reports of problems for beachcombers who may collect washed-up samples while unaware of their true nature.[16][17]

See also

References

  1. ^ Sigma-Aldrich Co., Phosphorus, white.
  2. ^ "White phosphorus". American Chemical Society. Retrieved 2024-08-10.
  3. doi:10.1021/ed009p11
    .
  4. ^
    ISBN 978-0-13-039913-7
    .
  5. ^
    ISBN 978-981-02-2634-3
    .
  6. ^
    doi:10.1002/cber.19971300911
    .
  7. PMID 20515032
    .
  8. LCCN 2003060796
    .
  9. ^ Threlfall, R.E., (1951). 100 years of Phosphorus Making: 1851–1951. Oldbury: Albright and Wilson Ltd
  10. ^
    ISBN 978-3-527-30385-4
    .
  11. ISBN 978-81-7450-648-1
    .
  12. ^
    ISBN 0-444-89307-5
    .
  13. doi:10.1002/anie.199504361
    .
  14. ^ Obscurants, National Research Council (US) Subcommittee on Military Smokes and (1999), "White Phosphorus Smoke", Toxicity of Military Smokes and Obscurants: Volume 2, National Academies Press (US), retrieved 2025-02-04
  15. ^ Toxicological Profile for White Phosphorous [sic] (PDF) (Report). U.S. Department of Health and Human Services. September 1997. Archived (PDF) from the original on 2025-01-18. Retrieved 2025-02-05.
  16. ^ Winter, George (1 October 2017). "A dangerous guide to beachcombing". Chemistry World.
  17. ^ Staudenmaier, Rebecca (May 8, 2017). "Woman mistakes WWII-era munition for precious stone on German beach | DW | 05.08.2017". Deutsche Welle.[dubious – discuss]
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