Phosphorus Pentachloride - PCl<sub>5</sub>

What is Phosphorus Pentachloride?

Phosphorus pentachloride is a pale greenish-yellow solid with the formula PCl5. Phosphorus pentachloride is known to have the salt-like structure in the crystalline state and to be partly dissociated in solution, especially in polar solvents such as nitrobenzene. It can be prepared by the action of dry chlorine on phosphorus trichloride. As per the law of mass action Phosphorus pentachloride vaporizes almost without dissociation in an atmosphere of chlorine gas or phosphorus trichloride, the dissociation equilibrium is shifted to the left by the presence of product.

Other names – Phosphorus(V) chloride, Pentachlorophosphorane


Phosphorus Pentachloride


2.1 g/cm³

Molecular Weight/ Molar Mass

208.24 g/mol

Boiling Point

166.8 °C

Melting Point

160.5 °C

Chemical Formula


Phosphorus Pentachloride Structure – PCl5

Phosphorus Pentachloride Structure

Physical Properties of Phosphorus Pentachloride – PCl5


Irritating odor


Greenish-yellow crystalline solid

Covalently-Bonded Unit


Molecular Geometry

Trigonal bipyramid




Soluble in water

Chemical Properties of Phosphorus Pentachloride – PCl5

  • Phosphorus pentachloride dissolves in water forming phosphoric acid and hydrogen chloride. The chemical reaction is given below.
  • PCl5 + 4H2O → H3PO4 + 5 HCl

  • Phosphorus pentachloride reacts with sulfur dioxide forms Phosphoryl chloride and Thionyl chloride.
  • SO2 + PCl5 → POCl3 + SOCl2

Uses of Phosphorus Pentachloride – PCl5

  • Used as a chlorinating agent and catalyst ш making organic chemicals, intermediates, dyestuffs, etc.
  • Used as a catalyst in the manufacture of acetyl cellulose the plastic film on which motion pictures are printed.
  • Used as a chlorinating agent in organic chemistry.
  • In pharmaceutical industry it is used in the manufacture of penicillin and cephalosporin.
  • Used to produce acid chlorides and as a catalyst for cyclisation and condensation reactions.

Leave a Comment

Your email address will not be published. Required fields are marked *