Preparation of Phosphorus and Its Compounds

When phosphorus atoms come into contact with oxygen atoms, ester groups are created. These have the ability to make bonds with carbon atoms, resulting in the formation of a diverse range of organic phosphorus compounds.

Phosphorus compounds can be found in a variety of forms in nature, with some of the most prevalent being phosphate rocks and minerals, bones, and teeth, among other things.

Phosphorus produces numerous halides with the halogen elements; the two simple series are PX₃ (in which X is F, Cl, Br, or I) and PX₅ (in which X is F, Cl, Br, or I). Rather than PX₅ molecules, the solids PCl₅ and PBr₅ contain PX₄⁺ cations and PX₆ anions. Organic phosphorus compounds are synthesised using these halides. Phosphorus combines with sulphur to generate a variety of sulphides, which are used to make organic compounds and matches. It forms phosphides when it reacts with a variety of metals and metalloids.

Phosphorus can be found in two different halides: PX₃ and PX₅. The most prevalent phosphorus halides are phosphorus pentachloride (PCl₅) and phosphorus trichloride (PC₃).

Phosphorus trichloride (PCl₃) -Phosphorus trichloride is a colourless, oily liquid that is extremely poisonous. The phosphorus is sp³ hybridized in the compound, which has a triangular pyramidal form.

PCl₃ is the chemical formula for phosphorus trichloride, an inorganic molecule. It is an essential industrial chemical that is used to make phosphites and other organophosphorus compounds. It is generally a white liquid when pure. 

Preparation

• Phosphorus trichloride is formed when dry chlorine is passed over hot white phosphorus.

P₄ + 6Cl₂ → 4PCl₃

• Phosphorus trichloride is formed when thionyl chloride combines with white phosphorus.

P + 8SOCl₂ → 4PCl₃ + 4SO₂ + 2S₂Cl₂

Chemical properties-

• In the presence of moisture, phosphorus trichloride hydrolysis to form phosphoric acid.

PCl₃ + 3H₂O → H₃PO₃ + 3HCl

• It produces chloro- derivatives from organic molecules bearing a –OH group.

3C₂H₅OH + PCl₃ → 3C₂H₅Cl + H₃PO₄

Phosphorus Pentachloride (PCl₅)^–

Phosphorus pentachloride is a water-sensitive yellowish-white solid. Carbon tetrachloride, carbon disulfide, benzene, hexane and diethyl ether are all soluble in it. In both gaseous and liquid states, it exhibits a trigonal bipyramidal structure. It exists as an ionic solid, [PCl₄]⁺ [PCl₆]^–, with the cation [PCl₄]⁺ being tetrahedral and the anion [PCl₆]^– being octahedral in solid form.

The production of three equatorial P-Cl bonds and two axial P-Cl bonds can be seen in the diagram. The two axial bonds are longer than the equatorial bonds due to stronger repulsion at axial positions compared to equatorial positions.

The phosphorus chlorides’ structures are always consistent with VSEPR theory. PCl₅‘s structure is influenced by its surroundings. PCl₅ is a neutral molecule with trigonal bipyramidal geometry and (D3h) symmetry that is gaseous and molten. The presence of non-bonding molecular orbitals (molecular orbital theory) or resonance can explain the hypervalent character of this species (valence bond theory). Nonpolar solvents like CS₂ and CCl₄ preserve this trigonal bipyramidal structure. PCl₅ is an ionic compound in the solid state, with the formula PCl + 4PCl.

Preparation-Phosphorus pentachloride prepared by reaction of white phosphorus with an excess of dry chlorine.

P₄ + 10Cl₂ → 4PCl₅

 It can also be made by combining SO₂Cl₂ and phosphorus in a reaction.

P₄ + 10SO₂Cl₂ → 4PCl₅ + 10SO₂

Chemical properties-Phosphorus pentachloride hydrolyzes to POCl₃ in wet air, which then transforms to phosphoric acid.

PCll₅ + H₂O → POCl₃ + 2HCl

POCl₃ + 3H₂O→H₃PO₄ + 3HCl

When heated, it sublimes and, if heated further, decomposes to phosphorus trichloride.

PCl₅ → PCl₃ + Cl₂

It produces metal chlorides by reacting with finely separated metals under the influence of heat.

2Ag + PCl₅ → 2AgCl + PCl₃

Uses of phosphorus halides

• It’s a chlorinating agent and an intermediary in the production of phosphorus acid, chloro-anhydrides, and phosphoric acid derivatives.

• It’s used to make organophosphorus insecticides, water treatment agents, lubricating oil, and paint additives, among other things.

Conclusion

With active metals, phosphorus (group 15) has an oxidation state of 3, and with more electronegative nonmetals, it has an oxidation state of 3+ and 5+. Phosphorus will be oxidised by halogens and oxygen. Phosphorus(V) oxide, P₄O₁₀, and phosphorus(III) oxide, P₄O₆, are the oxides. The reaction of a phosphate with sulfuric acid or the reaction of water with phosphorus(V) oxide are the two most popular ways to make orthophosphoric acid, H₃PO₄. Orthophosphoric acid is a triprotic acid that can be broken down into three different salts.