Interhalogen Compounds

Introduction

Interhalogen compounds are compounds formed when halogen group elements react with each other. In other words, it is a molecule which consists of two or more different elements of group 17. There are four types of interhalogen compounds:

  • Diatomic interhalogens (AX)

  • Tetratomic interhalogens (AX3)

  • Hexatomic interhalogens ( AX5)

  • Octatomic interhalogens (AX7)

A halogen with large size and high electropositivity reacts with an element of group 17 with small size and lower electropositivity. As the ratio of the radius of larger and smaller halogen increases, the number of atoms in a molecule also increases.

Preparation of Interhalogen compounds

These molecules are formed due to the direct combination or by the action of a group 17 element with a lower interhalogen compound under specific conditions. For example: At 437K, chlorine reacts with fluorine of equal volume to form ClF. This method is widely used in the production of group 17 fluorides.

Cl2 +F2 \(\rightarrow\) 2ClF (473K)

I2 + Cl2 \(\rightarrow\) 2ICl

Properties of Interhalogen Compounds

  • These molecules are covalent and diamagnetic in nature.
  • The bonds formed between these compounds are more reactive than diatomic halogen bonds.
  • The physical properties of these molecules are transitional between its constituents.
  • The molecular structure of AX3 molecules is bent T shaped, an AX5 molecule is square or pyramidal and the structure of AX7 is bipyramidal or pentagonal.
  • The bond length depends upon the size of the constituent halogens.
  • The molecule which consists of lighter group 17 elements is fairly colorless but one which is made up of higher halogens is deeper in color which is due to the rise in the molecular weight.

Uses of Interhalogen Compounds

  • These are used as non-aqueous solvents.
  • They are used as a catalyst in few reactions.
  • UF6 which is used in the enrichment of 235 U is produced by using ClF3 and BrF3.

U (s) + 3ClF3 (l) \(\rightarrow\) UF6 (g) + 3ClF (g)

  • These are used as fluorinating compounds.

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Structure and hybridisation of IF7