Phosphorus Triiodide(PI3) Properties(25 Quick Facts)

Phosphorous triiodide is an inorganic and tri-halogenated compound which is widely used for the conversion of alcohols to alkyl iodides. Let us look at some PI3 facts in detail.

Phosphorous triiodide is sp3 hybridized with the central atom being phosphorous and the surrounding atoms being the iodides. It is prepared by the addition of iodine to white phosphorous. It is used widely for the deprotection of alcohol to alkyl iodides.

In this article, we will discuss some basic properties of phosphorous like the melting point, boiling point, atomic radius, viscosity and odour in detail.

PI3 IUPAC name

The IUPAC (International union of pure and applied chemistry) name of PI3 is phosphorous triiodide or phosphorous (III) iodide.

PI3 chemical formula

The chemical formula of phosphorous triiodide is PI3. The valency of phosphorous is five out of which three electrons are bonded to iodine and has one lone pair.

PI3 CAS number

The CAS (Chemical abstract) number is 13455-01-1. It gives us information about the molecule.

PI3 ChemSpider ID

The ChemSpider ID of PI3 is 75323.

PI3 chemical classification

  • The chemical classification of a compound is based on the chemical properties that they possess. All the elements are divided into groups and periods based on their properties.
  • PI3 consists of Phosphorous and iodine where phosphorous belong to the Nitrogen family. In the nitrogen family elements contain three bond pairs and one lone pair and iodine belongs to the halogen family.

PI3 molar mass

The molar mass of phosphorous triiodide (PI3) is 411.687 g/mol. It is cumulative of Phosphorous and iodine.

PI3 colour

PI3 is a dark red solid in apppaerance.

PI3 viscosity

The viscosity of PI3 is 0.65cP.

PI3 molar density

The molar density of PI3 is 4.18 g/L. It is the ratio of the volume to the number of moles of the compound.

PI3 melting point

The melting point of PI3 is 61.2oC.

PI3 boiling point

The boiling point of PI3 is 200oC.

PI3 state at room temperature

PI3 is solid at room temperature.

PI3 covalent bond

PI3 has a covalent bond between phosphorous and iodine and a lone pair of electrons is also available on phosphorous for donation.

Pi3 covalent radius

The covalent radius of PI3 is 243pm. It is also the measure of the radius that forms the covalent bond.

Pi3 electron configurations

The electronic configuration is the way in which electrons are arranged in the different orbitals of an atom. Let us see the electronic configuration of phosphorous triiodide.

Phosphorous triiodide contains a Phosphorous atom having an electronic configuration of [Ne] 3s23p3. It also has iodine having the electronic configuration of [Kr] 4d105s25p5.

PI3 oxidation state

The oxidation state of phosphorous in PI3 is +3.

PI3 acidity/alkaline

PI3 is basic/alkaline in nature due to the presence of lone pairs of electrons.

Is PI3 odourless?

PI3 is odourless in nature.

Is PI3 paramagnetic?

Paramagnetic species are those which contain unpaired electrons and these are feebly attracted by the magnetic field. Let us see the paramagnetic nature of PI3.

PI3 is paramagnetic in nature. PI3 contains phosphorous and when we see the electronic configuration of phosphorous then there are no unpaired electrons as the p orbital is half-filled and in iodine, there is an unpaired electron because of which paramagnetism is seen in the compound.

PI3 hydrates

Phosphorous hydrates react with water to give phosphoric acid.


PI3 crystal structure

The crystal structure of PI3 is trigonal pyramidal in which the adjacent atoms occupy the corners of the pyramid hence the overall shape is trigonal pyramidal.

Phosphorous triiodide structure

PI3 polarity and conductivity

  • PI3 has no dipole moment. It is a non-polar compound.
  • PI3 is conductive in nature. As we can see from the electronic configuration there is a presence of unpaired electrons.

PI3 reaction with acid

PI3 reacts with acids to give acyl iodide and phosphoric acid.


PI3 reaction with base

PI3 reacts with base-like alcohol to give alkyl halide


B = (C2H5)2O, (C3H7)2O

If the basicity of ether is higher and the steric is less then the conversion of phosphorous iodide to diphosphorus iodide is easier. 

PI3 reaction with oxide

PI3 in reaction with oxygen does not give Phosphorous oxyiodide rather on oxidation with chlorine dioxide leads to the formation of iodine and phosphorous oxychloride.


PI3 reaction with metal

PI3 reacts with mercury to form a substance which is similar in composition to a trimethyl phosphine mercury diiodide complex.

PI3+ 3CH3I+Hg—>(CH3)3PHgI2


The chemistry of phosphorous halide is widely studied because of its vast use in organic chemistry. In this article, various chemical properties and their various reaction with metal, oxides and bases are discussed. This article gives brief information about all the properties of phosphorous.

Read more following properties

Aluminium hydrides
Aluminium Chemical Properties
Magnesium hydride(MgH2)
Phosphorus Triiodide(PI3)
Boron Chemical
Nitrogen Dioxide(NO2)
Phosphorus Trichloride(PCl3)
Sulfur Trioxide(SO3)
Carbon Tetrafluoride (CF4)
Propanoic Acid (CH3CH2COOH)
Barium Hydroxide(Ba(OH)2)
Silicon Chemical Properties
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