Diphosphorus pentoxide

Phosphorus pentoxide

Names
Other names Diphosphorus pentoxide Phosphorus(V) oxide Phosphoric anhydride Tetraphosphorus decaoxide Tetraphosphorus decoxide
Identifiers
CAS Number	1314-56-3 Y 16752-60-6 (P4O10) N
3D model (Jmol)	Interactive image
ChEBI	CHEBI:37376 Y
ChemSpider	14128 Y
ECHA InfoCard	100.013.852
PubChem	14812
RTECS number	TH3945000
InChI InChI=1S/P4O10/c1-11-5-12(2)8-13(3,6-11)10-14(4,7-11)9-12 N Key: DLYUQMMRRRQYAE-UHFFFAOYSA-N Y
SMILES O=P13OP2(=O)OP(=O)(O1)OP(=O)(O2)O3
Properties
Chemical formula	P4O10
Molar mass	283.886 g mol−1
Appearance	white powder very deliquescent pungent odour
Density	2.39 g/cm3
Melting point	sublimes
Boiling point	360 °C (680 °F; 633 K)
Solubility in water	exothermic hydrolysis
Vapor pressure	1 mmHg @ 385 °C (stable form)
Hazards
Safety data sheet	MSDS
EU classification (DSD)	not listed
NFPA 704	1 3 3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Phosphorus pentoxide is a chemical compound with molecular formula P₄O₁₀ (with its common name derived from its empirical formula, P₂O₅). This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desiccant and dehydrating agent.

Phosphorus pentoxide crystallizes in at least four forms or polymorphs. The most familiar one, a metastable form, shown in the figure, comprises molecules of P₄O₁₀. Weak van der Waals forces hold these molecules together in a hexagonal lattice (However, in spite of the high symmetry of the molecules, the crystal packing is not a close packing). The structure of the P₄O₁₀ cage is reminiscent of adamantane with T_dsymmetry point group. It is closely related to the corresponding anhydride of phosphorous acid, P₄O₆. The latter lacks terminal oxo groups. Its density is 2.30 g/cm³. It boils at 423 °C under atmospheric pressure; if heated more rapidly it can sublimate. This form can be made by condensing the vapor of phosphorus pentoxide rapidly, the result is an extremely hygroscopic solid.

The other polymorphs are polymeric, but in each case the phosphorus atoms are bound by a tetrahedron of oxygen atoms, one of which forms a terminal P=O bond involving the donation of the terminal oxygen p-orbital electrons to the antibonding phosphorus-oxygen single bonds. The macromolecular form can be made by heating the compound in a sealed tube for several hours, and maintaining the melt at a high temperature before cooling the melt to the solid. The metastable orthorhombic, "O"-form (density 2.72 g/cm³, melting point 562 °C), adopts a layered structure consisting of interconnected P₆O₆ rings, not unlike the structure adopted by certain polysilicates. The stable form is a higher density phase, also orthorhombic, the so-called O' form. It consists of a 3-dimensional framework, density 3.5 g/cm³. The remaining polymorph is a glass or amorphous form; it can be made by fusing any of the others.