5. Interhalogen compounds

Interhalogen compounds

We know that halogen atoms have different electronegativity. Due to this difference in electronegativity the halogen atoms combine with each other and give rise to the formation of binary covalent compounds, which are called interhalogen compounds. These are of four types.

Preparation :

Cl₂ + F₂ (equal volumes)  2ClF

Cl₂ + 3F₂ (excess)  2ClF₃ 

  I₂ + Cl₂ ® 2ICl ;

 (equimolar)

Diluted with water :   

Br₂ (g) + 3F₂ ® 2BrF₃

F₂ is diluted with N₂ :

I₂ + 3F₂  2IF₃

F₂ is taken in freon :

Br₂ + 5F₂ (excess)  ® 2BrF₅

  Properties :

(i)  These compounds may be gases, liquids or solids.

Gases : ClF, BrF, ClF₃ , IF₇

Liquids : BrF₃, BrF₅ 

Solids : ICl, IBr, IF₃, ICl₃.

(ii)  All interhalogens are covalent molecules and are diamagnetic in nature since all the valence electrons present as bonding or non-bonding electrons are paired.

(iii) The boiling points increases with the increase in the electronegativity difference between A and B atoms.

(iv) Interhalogen compounds are more reactive than the parent halogens but less reactive than F₂.

(v) Hydrolysis : All these undergo hydrolysis giving halide ion derived from the smaller halogen and a hypohalite (when AB), halite (when AB₃), halate (when AB₅), and perhalate (when AB₇) anion derived from the larger halogen.

AB + H₂O ® HB + HOA

BrCl + H₂O ® HCl + HOBr 

ICl + H₂O ® HCl + HIO₂

 Uses :

(i) These compounds can be used as non aqueous solvents.

(ii) Interhalogen compounds are very useful fluorinating agents.

(iii) ClF₃ and BrF₃ are used for the production of UF₆ in the enrichment of 235U.

 U(s) + 3 ClF₃ (l) ® UF₆ (g) + 3 ClF (g)