Phosphorus trioxide
{{Short description|Chemical compound}}
{{chembox
| Watchedfields = changed
| verifiedrevid = 444053776
| Name = Phosphorus(III) oxide
| ImageFile = Phosphorus-trioxide-from-xtal-3D-balls.png
| ImageName = Ball-and-stick model of the P4O6 molecule
| ImageCaption = Phosphorus in orange, oxygen in red
| ImageFile1 = Phosphorus-trioxide-xtal-3D-balls-A.png
| ImageName1 = Packing of P4O6 molecules in the crystal structure
| ImageFile2 = P4O6 photo (5).jpg
| ImageName2 = Liquid and solid phosphorus trioxide at its melting point
|IUPACName=Tetraphosphorus hexaoxide
Tricyclo[3.3.1.13,7]tetraphosphoxane
|SystematicName=2,4,6,8,9,10-Hexaoxa-1,3,5,7-tetraphosphatricyclo[3.3.1.13,7]decane
| OtherNames = Phosphorus sesquioxide
Phosphorous anhydride
Tetraphosphorous hexoxide
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 1314-24-5
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 37372
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 109897
| EC_number = 235-670-5
| Gmelin = 26856
| PubChem = 123290
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 0LTR52K7HK
| InChI = 1/O6P4/c1-7-2-9-4-8(1)5-10(3-7)6-9
| InChIKey = VSAISIQCTGDGPU-UHFFFAOYAV
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/O6P4/c1-7-2-9-4-8(1)5-10(3-7)6-9
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = VSAISIQCTGDGPU-UHFFFAOYSA-N
| SMILES = O1P3OP2OP(OP1O2)O3
}}
|Section2={{Chembox Properties
| Formula = P4O6
| MolarMass = 219.88 g mol−1
| Appearance = colourless monoclinic crystals or liquid
| Density = 2.135 g/cm3
| Solubility = reacts
| MeltingPtC = 23.8
| BoilingPtC = 173.1
| pKa = 9.4
| pKb =
}}
|Section3={{Chembox Structure
| MolShape = See Text
| CrystalStruct =
| Dipole = 0
}}
|Section7={{Chembox Hazards
| ExternalSDS =
| GHSPictograms = {{GHS06}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|}}
| PPhrases = {{P-phrases|}}
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 0
| GHS_ref =
}}
|Section8={{Chembox Related
| OtherAnions = Phosphorus trisulfide
| OtherCations = Dinitrogen trioxide
Arsenic trioxide
Antimony trioxide
| OtherCompounds = Phosphorus pentoxide
Phosphorous acid
}}
}}
Phosphorus trioxide is the chemical compound with the molecular formula P4O6. Although the molecular formula suggests the name tetraphosphorus hexoxide, the name phosphorus trioxide preceded the knowledge of the compound's molecular structure, and its usage continues today. This colorless solid is structurally related to adamantane. It is formally the anhydride of phosphorous acid, H3PO3, but cannot be obtained by the dehydration of the acid. A white solid that melts at room temperature, it is waxy, crystalline and highly toxic, with garlic odor.{{cite book |author1=A. F. Holleman |author2=Wiberg, Egon |author3=Wiberg, Nils |title=Inorganic Chemistry |publisher=Academic Press |location=Boston |year=2001 |isbn=0-12-352651-5 }}
Preparation
Chemical properties
Phosphorus trioxide reacts with water to form phosphorous acid, reflecting the fact that it is the anhydride of that acid.{{Greenwood&Earnshaw2nd}}
: P4O6 + 6 H2O → 4 H3PO3
It reacts with hydrogen chloride to form H3PO3 and phosphorus trichloride.
: P4O6 + 6 HCl → 2 H3PO3 + 2 PCl3
With chlorine or bromine it forms the corresponding phosphoryl halide, and it reacts with iodine in a sealed tube to form diphosphorus tetraiodide.
P4O6 reacts with ozone at 195 K to give the unstable compound P4O18..{{cite book
| title = Inorganic Chemistry, 3rd Edition
| chapter = Chapter 15: The group 15 elements
| author1 = Catherine E. Housecroft
| author2 = Alan G. Sharpe
| publisher = Pearson
| year = 2008
| isbn = 978-0-13-175553-6
| page = 473
}}
File:Reaction of phosphoprus trioxide with ozone.png
P4O18 decomposes above 238 K in solution with the release of O2 gas. Decomposition of dry P4O18 is explosive.
In a disproportionation reaction, P4O6 is converted into the mixed P(III)P(V) species P4O8 when heated in a sealed tube at 710 K, with the side product being red phosphorus.
As a ligand
File:Phosphorus-trioxide-iron-tetracarbonyl-complex-from-xtal-3D-balls.png
P4O6 is a ligand for transition metals, comparable to phosphite. An illustrative complex is P4O6·Fe(CO)4.{{ cite journal | journal = Acta Crystallogr. C | volume = 52 | issue = 11 |date=November 1996 | pages = 2650–2652 | doi = 10.1107/S0108270196004398 | title = Tetracarbonyl(tetraphosphorus hexoxide)iron |author1=M. Jansen |author2=J. Clade |name-list-style=amp | doi-access = free }}
With BH3, a dimeric adduct is produced:
References
{{Reflist}}
{{Phosphorus compounds}}
{{Oxides}}
{{DEFAULTSORT:Phosphorus Trioxide}}
Category:Adamantane-like molecules