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Phosphorus Trichloride

Phosphorus Trichloride is an inorganic compound that is usually a colourless liquid or slightly yellow liquid. It is an industrially important compound used in manufacturing several organophosphorus compounds.

Structure and Formula

The chemical formula of Phosphorus Trichloride is PCl3 and its structure is represented below.

Structure of Phosphorus Trichloride
Structure of the compound (Source)

In the structure of PCl3, three sp3 hybrid orbitals of P overlap with p-orbitals of Cl to form three P-Cl sigma bonds while the fourth sp3 hybrid orbital contains lone pair of electrons. Thus, PCl3 has a pyramidal structure.

Physical Properties

OdourPungent and irritating odour
AppearanceYellow fuming liquid (Colorless in pure form)
Melting point-93.6℃
Boiling point76.1℃
Density1.58
SolubilityHydrolyzes in water, soluble in benzene, ether, chloroform, CS2, CCl4, ethanol

Chemical Properties

Phosphorus trichloride on further chlorination gives phosphorus pentachloride.

PCl3 + Cl2 → PCl5

In water, the compound dissolves to form phosphoric acid and hydrogen chloride.

PCl3 + 3H2O → H3PO3 + 3HCl

Preparation

Following are a few ways to prepare PCl3:

  1. PCl3 is also be obtained when thionyl chloride reacts with white phosphorus.
    P4 + 8SOCl2 → 4PCl3 +4SO2 + S2Cl2
  2. The inorganic compound is prepared by passing dry chlorine gas over heated white phosphorus. Then the vapours of PCl3 ared distilled and are collected in receivers cooled by water.                                         
    P4 + 6Cl2 → 4PCl3

Applications

  • Phosphorus trichloride is a precursor to PCl5 and a few other phosphorus compounds, which is used in many applications, including herbicides, insecticides, oil additives, flame retardants, etc.
  • It is used directly as a reagent in organic synthesis.
  • It is mainly used for making phosphorus oxychloride by oxidizing it with oxygen.
  • It is also used during electrodeposition of metal on rubber.
  • It is also used for making pesticides, surfactants, gasoline additives, plasticizers, dyestuffs, textile finishing agents, germicides, medicinal products, and other chemicals

Hazards

The compound is highly toxic. It is fatal if swallowed or inhaled. Upon prolonged exposure, it causes damage to organs. Contact with the compound causes severe skin burns and eye damage.

FAQs

What is phosphorus trichloride used for?

It is used in gasoline additives, and textile finishing, and to make chemicals, pesticides, etc.

How is PCl3 formed?

The inorganic compound is prepared industrially by the reaction of chlorine with white phosphorus, using phosphorus trichloride as the solvent.

Is phosphorus trichloride ionic or covalent?

The compound has covalent bonding between P+3 and Cl ions.

More on Inorganic Compounds

Mohr’s Salt (Fe(SO4)(NH4)2(SO4)(H2O)6)Sodium Potassium Tartrate (C4H4O6KNa.4H2O)
Calcium Nitrate Ca(NO3)2Sulfur Trioxide (SO3)
Sodium Sulfate (Na2SO4)Ammonium Bicarbonate ((NH4)HCO3)
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