What is Phosphorus Pentoxide?

 What is Phosphorus Pentoxide?

Phosphorus pentoxide is a microcrystalline powder that is light in weight and white in appearance. This substance is the product of combustion, subjected to an excess supply of oxygen, of elemental phosphorus. The anhydride of H3PO4 (Orthophosphoric acid) is what is known as Phosphorus pentoxide. It is extremely hygroscopic where it is converted by H2O, using intermediates, into orthophosphoric acid (H3PO4). This compound’s reaction with H2O is extremely vigorous and a large amount of heat is produced when the reaction proceeds.

There are two chemical formulae for phosphorus pentoxide. P4O10 is the molecular formula while P2O5 is the empirical formula. At room temperature, the physical state of the compound is crystalline in nature and white in appearance. Phosphorus pentoxide is acquired from phosphoric acid as an acid anhydride. Due to its extremely hygroscopic nature, the compound proves to be quite useful as a desiccant and as a dehydrating medium.

Because of the microcrystalline and extremely hygroscopic nature of phosphorus pentoxide, the flow capability of P2O5 may vary in various ranges. Moreover, it is impossible to avoid the development of soft agglomerates that disintegrate under minimal pressure.

How is phosphorus pentoxide prepared?

Phosphorus pentoxide (P2O5 or P4O10) can be obtained by allowing tetra-phosphorus (elemental P4) to combust and be subjected to a liberal supply of oxygen. The formation of P2O5 is shown in a chemical reaction below:

P4 + 5O2> P4O10

This reaction gives out pure phosphorus pentoxide.

Chemical structure of Phosphorus Pentoxide

The structure of P2O5 (Phosphorus pentoxide) is given as 160 picometers is the P-O bond length and 143 is the P=O bond length.

Physical properties of Phosphorus Pentoxide (P2O5 or P4O10)

  • Phosphorus pentoxide does not have any particular odor and its physical appearance is a white solid.
  • P4O10 is the chemical formula for this substance. It is, nevertheless, called for its empirical formula, P2O5.
  • The density of phosphorus pentoxide is 2.39 g/cm3.
  • Phosphorus pentoxide has a molecular mass of 283.9 g/mol.
  • The boiling point of phosphorus pentoxide is 633K and its melting point is 613K.

Chemical properties of Phosphorus Pentoxide (P2O5 or P4O10)

  • When the compound is exposed to water, it will go through extreme hydrolysis and the reaction is extremely exothermic.
  • There are four polymorphs in which the compound crystallizes.
  • The compound can highly corrode metals and hence need to be stored away from metals.

Uses of Phosphorus pentoxide (P2O5)

  • Due to the hydrolysis procedure that takes place in an exothermic manner, phosphorus pentoxide is a very powerful dehydrating medium.
  • Some organic synthesis processes also employ phosphorus pentoxide. It’s utilized in the production of nitriles from primary amides.
  • It is commonly used in alcohol oxidation as it is an important component in the Onodera reagent.
  • Minerals acids can also be converted to their anhydrides using phosphorus pentoxide. As an example, we can obtain N2O5 from HNO3 using phosphorus pentoxide.

Applications of Phosphorus Pentoxide

Phosphorus pentoxide is popularly useful in the chemical market. It is used as a reagent as well as a building block.

  • Catalyst production

Catalysts supported by special phosphoric acid can be produced using phosphorus pentoxide (P2O5).

  • Production of glass

Phosphorus pentoxide is useful in the production of glass. It is also useful for obtaining boron trioxide and silicon dioxide as well.

  • Organic synthesis

As a condensation reagent, phosphorus pentoxide is useful in polymerization reactions as well as organic synthesis. Some of the common uses include ring closures/cyclization in reactions such as amine production, cyclic ketones, alkylation, acetylation, acid amides, oxygen or cyclic olefins, and sulfur heterocyclic compounds. In the pharmaceutical, vitamin, color, and dyes industries, these sorts of reactions are commonly employed to make organic intermediates.

  • Polyphosphoric acids

Polyphosphoric or super phosphoric acids of a wide range of grades can be produced by blending phosphoric acid and phosphorous pentoxide.

  • Drying agents

Due to its extremely hygroscopic nature, phosphorus pentoxide is a strong drying agent. The compound is a strong desiccant that may be used to dry acid and neutral gases, aromatic and aliphatic hydrocarbons, acryl, nitrites, alkyl halogenides, and carbon disulfide.

  • Special inorganic phosphates

Phosphorus pentoxide is a chemical that may be used to make sodium and ammonium phosphates. The inorganic compound ammonium phosphate has the formula (NH4)3PO4. It’s orthophosphoric acid’s ammonium salt. (NH4)3PO4 is a similar “double salt”. Sodium phosphate is a composition of phosphate anion and sodium cation. This salt can be found in anhydrous and hydrated salts out of which sodium phosphate can be found in nature more than ammonium phosphate.

  • Phosphate esters

Phosphate esters can be produced using phosphorus pentoxide by employing the use of mono/di ester content. This is accomplished by allowing the appropriate phenol or alcohol to react with the acid to obtain the desired product. Phosphate esters or organophosphates are a family of organophosphorus compounds that have the general formula O=P(OR)3, which consists of a core phosphate molecule with alkyl or aromatic substituents.

Reference for more concepts: the p-block elements from class 12 chemistry – find all the questions & answers

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