Iodine monochloride

Preparation

Iodine monochloride is produced simply by combining the halogens in a 1:1 molar ratio, according to the equation

:

When chlorine gas is passed through iodine crystals, one observes the brown vapor of iodine monochloride. Dark brown iodine monochloride liquid is collected. Excess chlorine converts iodine monochloride into iodine trichloride in a reversible reaction:

:

Polymorphs

has two polymorphs; α-ICl, which exists as black needles (red by transmitted light) with a melting point of 27.2 °C, and β-ICl, which exists as black platelets (red-brown by transmitted light) with a melting point 13.9 °C.

In the crystal structures of both polymorphs the molecules are arranged in zigzag chains. β-ICl is monoclinic with the space group P21/c.

Reactions and uses

Iodine monochloride is soluble in acids such as HF and HCl but reacts with pure water to form HCl, iodine, and iodic acid:

: + O2 : + O2 :

ICl is a useful reagent in organic synthesis. It also cleaves C–Si bonds.

ICl will also add to the double bond in alkenes to give chloro-iodo alkanes. :RCH=CHR′ + ICl → RCH(I)–CH(Cl)R′ When such reactions are conducted in the presence of sodium azide, the iodo-azide RCH(I)–CH(N3)R′ is obtained.

The Wijs solution, iodine monochloride dissolved in acetic acid, is used to determine the iodine value of a substance.

It can also be used to prepare iodates, by reaction with a chlorate. Chlorine is released as a byproduct.

Iodine monochloride is a Lewis acid that forms 1:1 adducts with Lewis bases such as dimethylacetamide and benzene.

References

References

1. {{Greenwood&Earnshaw2nd
2. (2004). "Encyclopedia of Reagents for Organic Synthesis".
3. Carpenter, G. B.. (1 April 1962). "The crystal structure of β-iodine monochloride". Acta Crystallographica.
4. Wallingford, V. H.. (1943). "5-Iodo-anthranilic Acid".
5. Padwa, A.. "3-Phenyl-2H-Azirine-2-carboxaldehyde".