Phosphorus pentoxide

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Phosphorus pentoxide
Phosphorus pentoxide Phosphorus-pentoxide-2D-dimensions.svg
Phosphorus pentoxide
Phosphorus pentoxide Phosphorus-pentoxide-3D-balls.png
Phosphorus pentoxide
Sample of Phosphorus pentoxide.jpg
Names
IUPAC names
Tetraphosphorus decaoxide
Tricyclo[3.3.1.13,7]tetraphosphoxane 1,3,5,7-tetraoxide
Systematic IUPAC name
2,4,6,8,9,10-Hexaoxa-1λ5,3λ5,5λ5,7λ5-tetraphosphatricyclo[3.3.1.13,7]decane 1,3,5,7-tetraoxide
Other names
Diphosphorus pentoxide
Phosphorus(V) oxide
Phosphoric anhydride
Tetraphosphorus decaoxide
Tetraphosphorus decoxide
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.013.852 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
RTECS number
  • TH3945000
UNII
  • InChI=1S/O10P4/c1-11-5-12(2)8-13(3,6-11)10-14(4,7-11)9-12 Yes check.svgY
    Key: DLYUQMMRRRQYAE-UHFFFAOYSA-N Yes check.svgY
  • molecular form:O=P13OP2(=O)OP(=O)(O1)OP(=O)(O2)O3
  • crystal o′ form:P12(=O)OP3(=O)OP4(=O)OP5(=O)OP6(=O)OP(=O)(O1)OP7(=O)OP(=O)OP(=O)OP(=O)(O2)OP(=O)OP(=O)OP(=O)(O3)OP(=O)OP(=O)OP(=O)(O4)OP(=O)OP(=O)OP(=O)(O5)OP(=O)OP(=O)OP(=O)(O6)OP(=O)OP(=O)(O7)O
Properties
P4O10
Molar mass 283.9 g mol−1
AppearanceWhite powder
Very deliquescent
Odor Odorless
Density 2.39 g/cm3
Melting point 340 °C (644 °F; 613 K)
Boiling point 360 °C (sublimes)
exothermic hydrolysis
Vapor pressure 1 mmHg @ 385 °C (stable form)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 reacts with water, strong dehydrating agent, corrosive
GHS labelling:
GHS-pictogram-acid.svg
Danger
H314
P280, P301+P330+P331, P303+P361+P353, P305+P351+P338, P310
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
3
0
3
W
Safety data sheet (SDS) MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Phosphorus pentoxide is a chemical compound with molecular formula P 4 O 10 (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.

Contents

Structure

Phosphorus pentoxide crystallizes in at least four forms or polymorphs. The most familiar one, a metastable form [1] (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 [2] ). The structure of the P4O10 cage is reminiscent of adamantane with Td symmetry point group. [3] 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, and the result is an extremely hygroscopic solid. [4]

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. [4] 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. [1] [5] The remaining polymorph is a glass or amorphous form; it can be made by fusing any of the others.

Phosphorus-pentoxide-sheet-from-xtal-3D-balls.png
Phosphorus-pentoxide-xtal-3D-balls.png
Part of an o′-(P2O5)∞ layero′-(P2O5)∞ layers stacking

Preparation

P4O10 is prepared by burning white phosphorus with a sufficient supply of oxygen: [6]

P4 + 5 O2 → P4O10

The dehydration of phosphoric acid to give phosphorus pentoxide is not possible, as on heating it forms various polyphosphates but will not dehydrate sufficiently to form P4O10.

Applications

Phosphorus pentoxide is a potent dehydrating agent as indicated by the exothermic nature of its hydrolysis producing phosphoric acid:

P4O10 + 6 H2O → 4 H3PO4  (–177 kJ)

However, its utility for drying is limited somewhat by its tendency to form a protective viscous coating that inhibits further dehydration by unspent material. A granular form of P4O10 is used in desiccators.

Consistent with its strong desiccating power, P4O10 is used in organic synthesis for dehydration. The most important application is for the conversion of primary amides into nitriles: [7]

P4O10 + RC(O)NH2 → P4O9(OH)2 + RCN

The indicated coproduct P4O9(OH)2 is an idealized formula for undefined products resulting from the hydration of P4O10.

Alternatively, when combined with a carboxylic acid, the result is the corresponding anhydride: [8]

P4O10 + RCO2H → P4O9(OH)2 + [RC(O)]2O

The "Onodera reagent", a solution of P4O10 in DMSO, is employed for the oxidation of alcohols. [9] This reaction is reminiscent of the Swern oxidation.

The desiccating power of P4O10 is strong enough to convert many mineral acids to their anhydrides. Examples: HNO3 is converted to N2O5;  H2SO4 is converted to SO3;  HClO4 is converted to Cl2O7;  CF3SO3H is converted to (CF3)2S2O5.

As a proxy measurement

P2O5 content is often used by industry as proxy value for all the phosphorus oxides in a material. For example, fertilizer grade phosphoric acid can also contain various related phosphorous compounds which are also of use. All these compounds are described collectively in terms of 'P2O5 content' to allow convenient comparison of the phosphorous content of different products. Despite this, phosphorus pentoxide is not actually present in most samples as it is not stable in aqueous solutions.

Between the commercially important P4O6 and P4O10, phosphorus oxides are known with intermediate structures. [10]

Structures of phosphorus oxides edit.png

On observation it will be seen that double bonded oxygen in at 1,2 position or 1,3 position are identical and both positions have same steric hindrance. Cycle 12341 and ABCDA are identical.

Hazards

Phosphorus pentoxide itself is not flammable. Just like sulfur trioxide, it reacts vigorously with water and water-containing substances like wood or cotton, liberates much heat and may even cause fire due to the highly exothermic nature of such reactions. It is corrosive to metal and is very irritating – it may cause severe burns to the eye, skin, mucous membrane, and respiratory tract even at concentrations as low as 1 mg/m3. [11]

See also

Related Research Articles

<span class="mw-page-title-main">Phosphorus</span> Chemical element, symbol P and atomic number 15

Phosphorus is a chemical element; it has symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Earth. It has a concentration in the Earth's crust of about one gram per kilogram. In minerals, phosphorus generally occurs as phosphate.

<span class="mw-page-title-main">Copper(II) nitrate</span> Chemical compound

Copper(II) nitrate describes any member of the family of inorganic compounds with the formula Cu(NO3)2(H2O)x. The hydrates are blue solids. Anhydrous copper nitrate forms blue-green crystals and sublimes in a vacuum at 150-200 °C. Common hydrates are the hemipentahydrate and trihydrate.

<span class="mw-page-title-main">Dinitrogen pentoxide</span> Chemical compound

Dinitrogen pentoxide is the chemical compound with the formula N2O5. It is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen. It exists as colourless crystals that sublime slightly above room temperature, yielding a colorless gas.

An acidic oxide is an oxide that either produces an acidic solution upon addition to water, or acts as an acceptor of hydroxide ions effectively functioning as a Lewis acid. Acidic oxides will typically have a low pKa and may be inorganic or organic. A commonly encountered acidic oxide, carbon dioxide produces an acidic solution when dissolved.

<span class="mw-page-title-main">Organic acid anhydride</span> Any chemical compound having two acyl groups bonded to the same oxygen atom

An organic acid anhydride is an acid anhydride that is also an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O))2O. Symmetrical acid anhydrides of this type are named by replacing the word acid in the name of the parent carboxylic acid by the word anhydride. Thus, (CH3CO)2O is called acetic anhydride.Mixed (or unsymmetrical) acid anhydrides, such as acetic formic anhydride (see below), are known, whereby reaction occurs between two different carboxylic acids. Nomenclature of unsymmetrical acid anhydrides list the names of both of the reacted carboxylic acids before the word "anhydride" (for example, the dehydration reaction between benzoic acid and propanoic acid would yield "benzoic propanoic anhydride").

<span class="mw-page-title-main">Dichlorine heptoxide</span> Chemical compound

Dichlorine heptoxide is the chemical compound with the formula Cl2O7. This chlorine oxide is the anhydride of perchloric acid. It is produced by the careful distillation of perchloric acid in the presence of the dehydrating agent phosphorus pentoxide:

<span class="mw-page-title-main">Phosphoric acids and phosphates</span> Class of chemical species; phosphorus oxoacids and their deprotonated derivatives

In chemistry, a phosphoric acid, in the general sense, is a phosphorus oxoacid in which each phosphorus (P) atom is in the oxidation state +5, and is bonded to four oxygen (O) atoms, one of them through a double bond, arranged as the corners of a tetrahedron. Two or more of these PO4 tetrahedra may be connected by shared single-bonded oxygens, forming linear or branched chains, cycles, or more complex structures. The single-bonded oxygen atoms that are not shared are completed with acidic hydrogen atoms. The general formula of a phosphoric acid is Hn+2−2xPnO3n+1−x, where n is the number of phosphorus atoms and x is the number of fundamental cycles in the molecule's structure, between 0 and n + 2/2.

<span class="mw-page-title-main">Iodic acid</span> Chemical compound (HIO3)

Iodic acid is a white water-soluble solid with the chemical formula HIO3. Its robustness contrasts with the instability of chloric acid and bromic acid. Iodic acid features iodine in the oxidation state +5 and is one of the most stable oxo-acids of the halogens. When heated, samples dehydrate to give iodine pentoxide. On further heating, the iodine pentoxide further decomposes, giving a mix of iodine, oxygen and lower oxides of iodine.

In chemistry, phosphorus oxoacid is a generic name for any acid whose molecule consists of atoms of phosphorus, oxygen, and hydrogen. There is a potentially infinite number of such compounds. Some of them are unstable and have not been isolated, but the derived anions and organic groups are present in stable salts and esters. The most important ones—in biology, geology, industry, and chemical research—are the phosphoric acids, whose esters and salts are the phosphates.

Hypophosphorous acid (HPA), or phosphinic acid, is a phosphorus oxyacid and a powerful reducing agent with molecular formula H3PO2. It is a colorless low-melting compound, which is soluble in water, dioxane and alcohols. The formula for this acid is generally written H3PO2, but a more descriptive presentation is HOP(O)H2, which highlights its monoprotic character. Salts derived from this acid are called hypophosphites.

<span class="mw-page-title-main">Phosphoryl chloride</span> Chemical compound

Phosphoryl chloride is a colourless liquid with the formula POCl3. It hydrolyses in moist air releasing phosphoric acid and fumes of hydrogen chloride. It is manufactured industrially on a large scale from phosphorus trichloride and oxygen or phosphorus pentoxide. It is mainly used to make phosphate esters.

<span class="mw-page-title-main">Phosphorus trioxide</span> Chemical compound

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.

Deoxygenation is a chemical reaction involving the removal of oxygen atoms from a molecule. The term also refers to the removal of molecular oxygen (O2) from gases and solvents, a step in air-free technique and gas purifiers. As applied to organic compounds, deoxygenation is a component of fuels production as well a type of reaction employed in organic synthesis, e.g. of pharmaceuticals.

<span class="mw-page-title-main">Methanesulfonic anhydride</span> Chemical compound

Methanesulfonic anhydride (Ms2O) is the acid anhydride of methanesulfonic acid. Like methanesulfonyl chloride (MsCl), it may be used to generate mesylates (methanesulfonyl esters).

<span class="mw-page-title-main">Trifluoroacetic anhydride</span> Chemical compound

Trifluoroacetic anhydride (TFAA) is the acid anhydride of trifluoroacetic acid. It is the perfluorinated derivative of acetic anhydride.

Phosphorus oxide can refer to:

<span class="mw-page-title-main">Phosphoryl bromide</span> Chemical compound

Phosphoryl bromide, also known as phosphorus oxybromide, is an inorganic compound with the formula POBr3.

<span class="mw-page-title-main">Hypophosphoric acid</span> Chemical compound

Hypophosphoric acid is a mineral acid with the formula H4P2O6, with phosphorus in a formal oxidation state of +4. In the solid state it is present as the dihydrate, H4P2O6·2H2O. In hypophosphoric acid the phosphorus atoms are identical and joined directly with a P−P bond. Isohypophosphoric acid is a structural isomer of hypophosphoric acid in which one phosphorus has a hydrogen directedly bonded to it and that phosphorus atom is linked to the other one by an oxygen bridge to give a phosphorous acid/phosphoric acid mixed anhydride. The two phosphorus atoms are in the +3 and +5 oxidation states, respectively.

<span class="mw-page-title-main">Diethylphosphite</span> Chemical compound

Diethyl phosphite is the organophosphorus compound with the formula (C2H5O)2P(O)H. It is a popular reagent for generating other organophosphorus compounds, exploiting the high reactivity of the P-H bond. Diethyl phosphite is a colorless liquid. The molecule is tetrahedral.

<span class="mw-page-title-main">Peroxymonophosphoric acid</span> Oxyacid of phosphorus

Peroxymonophosphoric acid is an oxyacid of phosphorus. It is a colorless viscous oil. Its salts are called peroxymonophosphates. Another peroxyphosphoric acid is peroxydiphosphoric acid, H4P2O8.

References

  1. 1 2 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  2. ↑ Cruickshank, D. W. J. (1964). "Refinements of Structures Containing Bonds between Si, P, S or Cl and O or N: V. P4O10". Acta Crystallogr. 17 (6): 677–9. doi: 10.1107/S0365110X64001669 .
  3. ↑ D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam. ISBN   0-444-89307-5.
  4. 1 2 .Catherine E. Housecroft; Alan G. Sharpe (2008). "Chapter 15: The group 15 elements". Inorganic Chemistry, 3rd Edition. Pearson. p. 473. ISBN   978-0-13-175553-6.
  5. ↑ D. Stachel, I. Svoboda and H. Fuess (June 1995). "Phosphorus Pentoxide at 233 K". Acta Crystallogr. C. 51 (6): 1049–1050. doi:10.1107/S0108270194012126.
  6. ↑ Threlfall, Richard E., (1951). The story of 100 years of Phosphorus Making: 1851 - 1951. Oldbury: Albright & Wilson Ltd
  7. ↑ Meier, M. S. "Phosphorus(V) Oxide" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi : 10.1002/047084289X.
  8. ↑ Joseph C. Salamone, ed. (1996). Polymeric materials encyclopedia: C, Volume 2. CRC Press. p. 1417. ISBN   0-8493-2470-X.
  9. ↑ Tidwell, T. T. "Dimethyl Sulfoxide–Phosphorus Pentoxide" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi : 10.1002/047084289X.
  10. ↑ Luer, B.; Jansen, M. "Crystal Structure Refinement of Tetraphosphorus Nonaoxide, P4O9" Zeitschrift für Kristallographie 1991, volume 197, pages 247-8.
  11. ↑ Phosphorus pentoxide MSDS
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