Phosphorus Pentachloride

What is Phosphorus Pentachloride?

Phosphorus pentachloride is a greenish-yellow crystalline solid, It is decomposed by water to form hydrochloric acid and phosphoric acid with the release of heat energy. It can also be prepared by the action of dry chlorine on phosphorus trichloride. The chemical formula for phosphorus pentachloride is PCl₅. In solid-state, it exists as [PCl₄]⁺ [PCl₆]⁻ .

Phosphorus pentachloride vaporizes without dissociation in an atmosphere phosphorus trichloride or chlorine gas. The dissociation equilibrium is shifted to the left side by the presence of the product.

Structure of Phosphorus Pentachloride

The hybridization in phosphorus pentachloride is sp³d and it has a trigonal bipyramidal geometry in gaseous and liquid states. It has two axial P−Cl bonds and three equatorial P−Cl bonds.

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Properties of Phosphorus Pentachloride

Uses of Phosphorus Pentachloride (PCl₅)

• It is used as a chlorinating agent.

• It is used for the manufacture of penicillin and cephalosporin in the pharmaceutical industry.

• Used to produce acid chlorides. 

• Used as a catalyst in the manufacture of acetyl cellulose and also a catalyst for condensation reactions and cyclization.

Methods of Preparation of Phosphorus Pentachloride (PCl₅)

• P₄ + 10SO₂Cl₂ → 4PCl₅ + 10SO₂ 

• P₄ + 10Cl₂ → 4PCl₅

• PCl₃ + Cl₂ → PCl₅

Chemical Properties of Phosphorus Pentachloride (PCl₅)

• Phosphorus pentachloride dissociates as: PCl₅ ⇌ PCl₃ + Cl₂

• Reaction with water: PCl₅ + 4H₂O → H₃PO₄ + 5HCl

• Reaction with metal: Zn + PCl₅ → ZnCl₂ + PCl₃

• Reactions with phosphorus pentoxide: 6PCl₅ + P₄O₁₀ → 10POCl₃ 

• Reactions with sulfur dioxide: SO₂ + PCl₅ → POCl₃ + SOCl₂ 

Harmful Effects of Phosphorus Pentachloride

Phosphorus Pentachloride is a Reactive Chemical. Direct exposure to Phosphorus Pentachloride can cause weakness, nausea, headache, dizziness, and vomiting. It may damage the liver and kidneys.