Iodine monochloride

Iodine monochloride
I-Cl bond length = 232.07 pm	Space-filling model
Names
	Preferred IUPAC name Iodine monochloride; Iodine(I) chloride
	Systematic IUPAC name Chloroiodane
	Other names Iodine chloride
Identifiers
CAS Number	7790-99-0 ;
3D model (JSmol)	Interactive image;
ChemSpider	23042 ;
ECHA InfoCard	100.029.306
EC Number	232-236-7;
MeSH	Iodine-monochloride
PubChem CID	24640;
UNII	0SMG5NLU45 ;
UN number	1792
CompTox Dashboard (EPA)	DTXSID1064879 ;
	InChI InChI=1S/ClI/c1-2 Key: QZRGKCOWNLSUDK-UHFFFAOYSA-N ; InChI=1S/ClI/c1-2 Key: QZRGKCOWNLSUDK-UHFFFAOYSA-N; InChI=1/ClI/c1-2 Key: QZRGKCOWNLSUDK-UHFFFAOYAO;
	SMILES ClI;
Properties
Chemical formula	ICl
Molar mass	162.35 g/mol
Appearance	reddish-brown
Density	3.10 g/cm3
Melting point	27.2 °C (81.0 °F; 300.3 K) (α-form); 13.9 °C (β-form)
Boiling point	97.4 °C (207.3 °F; 370.5 K)
Solubility in water	Hydrolyzes
Solubility	soluble in CS2; acetic acid; pyridine ; alcohol, ether, HCl
Magnetic susceptibility (χ)	−54.6×10−6 cm3/mol
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Corrosive, reacts with water to release HCl
Safety data sheet (SDS)	https://chemicalsafety.com/sds1/sdsviewer.php?id=30683304
Related compounds
Related interhalogen compounds	Chlorine monofluoride; Bromine monochloride; Iodine monobromide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Iodine monochloride is an interhalogen compound with the formula ICl. It is a red-brown chemical compound that melts near room temperature. Because of the difference in the electronegativity of iodine and chlorine, this molecule is highly polar and behaves as a source of I⁺. Discovered in 1814 by Gay-Lussac, iodine monochloride is the first interhalogen compound discovered.^[1]

Preparation

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

I₂ + Cl₂ → 2 ICl

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:

ICl + Cl₂ ⇌ ICl₃

Polymorphs

ICl 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.^[2]

In the crystal structures of both polymorphs the molecules are arranged in zigzag chains. β-ICl is monoclinic with the space group P2₁/c.^[3]

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:

ICl + H₂O → HCl + HI + 1⁄2O₂

2 ICl + H₂O → 2 HCl + I₂ + 1⁄2O₂

5 ICl + 3 H₂O → 5 HCl + HIO₃ + 2 I₂

ICl is a useful reagent in organic synthesis.^[2] It is used as a source of electrophilic iodine in the synthesis of certain aromatic iodides.^[4] 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.^[5]

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

^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 790. ISBN 978-0-08-037941-8.
^ ^a ^b Brisbois, R. G.; Wanke, R. A.; Stubbs, K. A.; Stick, R. V. "Iodine Monochloride" Encyclopedia of Reagents for Organic Synthesis, 2004 John Wiley & Sons. doi:10.1002/047084289X.ri014
^ Carpenter, G. B.; Richards, S. M. (1 April 1962). "The crystal structure of β-iodine monochloride". Acta Crystallographica. 15 (4): 360–364. doi:10.1107/S0365110X62000882.
^ Wallingford, V. H.; Krüger, P. A. (1943). "5-Iodo-anthranilic Acid". Organic Syntheses; Collected Volumes, vol. 2, p. 349.
^ Padwa, A.; Blacklock, T.; Tremper, A. "3-Phenyl-2H-Azirine-2-carboxaldehyde". Organic Syntheses; Collected Volumes, vol. 6, p. 893.

[1] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 790. ISBN 978-0-08-037941-8.

[Bris-2] Brisbois, R. G.; Wanke, R. A.; Stubbs, K. A.; Stick, R. V. "Iodine Monochloride" Encyclopedia of Reagents for Organic Synthesis, 2004 John Wiley & Sons. doi:10.1002/047084289X.ri014

[3] Carpenter, G. B.; Richards, S. M. (1 April 1962). "The crystal structure of β-iodine monochloride". Acta Crystallographica. 15 (4): 360–364. doi:10.1107/S0365110X62000882.

[4] Wallingford, V. H.; Krüger, P. A. (1943). "5-Iodo-anthranilic Acid". Organic Syntheses; Collected Volumes, vol. 2, p. 349.

[5] Padwa, A.; Blacklock, T.; Tremper, A. "3-Phenyl-2H-Azirine-2-carboxaldehyde". Organic Syntheses; Collected Volumes, vol. 6, p. 893.

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