Iodine monochloride

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Iodine monochloride
I-Cl bond length = 232.07 pm Iodine-monochloride-2D.png
I-Cl bond length = 232.07 pm
Space-filling model Iodine-monochloride-3D-vdW.png
Space-filling model
Iodine monochloride1.jpg
Preferred IUPAC name
Iodine monochloride
Iodine(I) chloride
Systematic IUPAC name
Other names
Iodine chloride
3D model (JSmol)
ECHA InfoCard 100.029.306 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 232-236-7
MeSH Iodine-monochloride
PubChem CID
UN number 1792
  • InChI=1S/ClI/c1-2 Yes check.svgY
  • InChI=1S/ClI/c1-2
  • InChI=1/ClI/c1-2
  • ClI
Molar mass 162.35 g/mol
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 soluble in CS2
acetic acid
alcohol, ether, HCl
−54.6×10−6 cm3/mol
Occupational safety and health (OHS/OSH):
Main hazards
Corrosive, reacts with water to release HCl
Safety data sheet (SDS) External MSDS
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).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

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+.



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


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. [1]

In the crystal structures of both polymorphs the molecules are arranged in zigzag chains. β-ICl is monoclinic with the space group P21/c. [2]

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 + 12O2
2 ICl + H2O → 2 HCl + I2 + 12O2
5 ICl + 3 H2O → 5 HCl + HIO3 + 2 I2

ICl is a useful reagent in organic synthesis. [1] It is used as a source of electrophilic iodine in the synthesis of certain aromatic iodides. [3] 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. [4]

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.

Related Research Articles

Iodine Chemical element, symbol I and atomic number 53

Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at 114 °C (237 °F), and boils to a violet gas at 184 °C (363 °F). The element was discovered by the French chemist Bernard Courtois in 1811 and was named two years later by Joseph Louis Gay-Lussac, after the Ancient Greek Ιώδης 'violet-coloured'.

Haloalkane Group of chemical compounds derived from alkanes containing one or more halogens

The haloalkanes are alkanes containing one or more halogen substituents. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially. They are used as flame retardants, fire extinguishants, refrigerants, propellants, solvents, and pharmaceuticals. Subsequent to the widespread use in commerce, many halocarbons have also been shown to be serious pollutants and toxins. For example, the chlorofluorocarbons have been shown to lead to ozone depletion. Methyl bromide is a controversial fumigant. Only haloalkanes that contain chlorine, bromine, and iodine are a threat to the ozone layer, but fluorinated volatile haloalkanes in theory may have activity as greenhouse gases. Methyl iodide, a naturally occurring substance, however, does not have ozone-depleting properties and the United States Environmental Protection Agency has designated the compound a non-ozone layer depleter. For more information, see Halomethane. Haloalkane or alkyl halides are the compounds which have the general formula "RX" where R is an alkyl or substituted alkyl group and X is a halogen.

Trichlorosilane Chemical compound

Trichlorosilane is an inorganic compound with the formula HCl3Si. It is a colourless, volatile liquid. Purified trichlorosilane is the principal precursor to ultrapure silicon in the semiconductor industry. In water, it rapidly decomposes to produce a silicone polymer while giving off hydrochloric acid. Because of its reactivity and wide availability, it is frequently used in the synthesis of silicon-containing organic compounds.

Manganese dioxide Chemical compound

Manganese dioxide is the inorganic compound with the formula MnO
. This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for MnO
is for dry-cell batteries, such as the alkaline battery and the zinc–carbon battery. MnO
is also used as a pigment and as a precursor to other manganese compounds, such as KMnO
. It is used as a reagent in organic synthesis, for example, for the oxidation of allylic alcohols. MnO
is α polymorph that can incorporate a variety of atoms in the "tunnels" or "channels" between the manganese oxide octahedra. There is considerable interest in α-MnO
as a possible cathode for lithium-ion batteries.

Iron(III) chloride Inorganic compound

Iron(III) chloride is the inorganic compound with the formula FeCl3. Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The color depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red.

In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. This kind of conversion is in fact so common that a comprehensive overview is challenging. This article mainly deals with halogenation using elemental halogens (F2, Cl2, Br2, I2). Halides are also commonly introduced using salts of the halides and halogen acids. Many specialized reagents exist for and introducing halogens into diverse substrates, e.g. thionyl chloride.

Hydrogen bromide Chemical compound

Hydrogen bromide is the inorganic compound with the formula HBr. It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room temperature. Aqueous solutions that are 47.6% HBr by mass form a constant-boiling azeotrope mixture that boils at 124.3 °C. Boiling less concentrated solutions releases H2O until the constant-boiling mixture composition is reached.

In chemistry, an interhalogen compound is a molecule which contains two or more different halogen atoms and no atoms of elements from any other group.

Aluminium chloride Chemical compound

Aluminium chloride (AlCl3), also known as aluminium trichloride, describe compounds with the formula AlCl3(H2O)n (n = 0 or 6). They consist of aluminium and chlorine atoms in a 1:3 ratio, and one form also contains six waters of hydration. Both are white solids, but samples are often contaminated with iron(III) chloride, giving a yellow color.

Oxalyl chloride Chemical compound

Oxalyl chloride is a chemical compound with the formula (COCl)2. This colorless, sharp-smelling liquid, the diacyl chloride of oxalic acid, is a useful reagent in organic synthesis.

Triphenylphosphine Chemical compound

Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature. It dissolves in non-polar organic solvents such as benzene and diethyl ether.

Trimethylsilyl chloride Chemical compound

Trimethylsilyl chloride, also known as chlorotrimethylsilane is an organosilicon compound (silyl halide), with the formula (CH3)3SiCl, often abbreviated Me3SiCl or TMSCl. It is a colourless volatile liquid that is stable in the absence of water. It is widely used in organic chemistry.

Sulfonyl halide groups occur when a sulfonyl functional group is singly bonded to a halogen atom. They have the general formula RSO2X where X is a halogen. The stability of sulfonyl halides decreases in the order fluorides > chlorides > bromides > iodides, all four types being well known. The sulfonyl chlorides and fluorides are of dominant importance in this series.

Iodane generally refers to any organic derivative of iodine. Without modifier, iodane is the systematic name for the parent hydride of iodine, HI. Thus, any organoiodine compound with general formula RI is a substituted iodane. However, as used in the context of organic synthesis, the term iodane more specifically refers to organoiodine compounds with nonstandard bond number, making this term a synonym for hypervalent iodine. These iodine compounds are hypervalent because the iodine atom formally contains more than the 8 electrons in the valence shell required for the octet rule. When iodine is ligated to an organic residue and electronegative ligands, hypervalent iodine compounds occur with a +3 oxidation number as iodine(III) or λ3-iodanes, or as a +5 oxidation number as iodine(V) or λ5-iodanes, or as a +7 oxidation number as iodine(VII) or λ7-iodanes.

Iodobenzene dichloride (PhICl2) is a complex of iodobenzene with chlorine. As a reagent for organic chemistry, it is used as an oxidant and chlorinating agent.

Selenium monochloride Chemical compound

Selenium monochloride is an inorganic compound with the formula Se2Cl2. Although it is called selenium monochloride, a more descriptive name might be diselenium dichloride. It is a reddish-brown, oily liquid that hydrolyses slowly. It exists in chemical equilibrium with SeCl2, SeCl4, chlorine, and elemental selenium. Selenium monochloride is mainly used as a reagent for the synthesis of Se-containing compounds.

Vinyl iodide functional group

In organic chemistry, a vinyl iodide functional group is an alkene with one or more iodide substituents. Vinyl iodides are versatile molecules that serve as important building blocks and precursors in organic synthesis. They are commonly used in carbon-carbon forming reactions in transition-metal catalyzed cross-coupling reactions, such as Stille reaction, Heck reaction, Sonogashira coupling, and Suzuki coupling. Synthesis of well-defined geometry or complexity vinyl iodide is important in stereoselective synthesis of natural products and drugs.

Imidoyl chloride

Imidoyl chlorides are organic compounds that contain the functional group RC(NR')Cl. A double bond exist between the R'N and the carbon centre. These compounds are analogues of acyl chloride. Imidoyl chlorides tend to be highly reactive and are more commonly found as intermediates in a wide variety of synthetic procedures. Such procedures include Gattermann aldehyde synthesis, Houben-Hoesch ketone synthesis, and the Beckmann rearrangement. Their chemistry is related to that of enamines and their tautomers when the α hydrogen is next to the C=N bond. Many chlorinated N-heterocycles are formally imidoyl chlorides, e.g. 2-chloropyridine, 2, 4, and 6-chloropyrimidines.

(Diacetoxyiodo)benzene Chemical compound

(Diacetoxyiodo)benzene, also known as phenyliodine(III) diacetate (PIDA) is a hypervalent iodine chemical with the formula C
. It is used as an oxidizing agent in organic chemistry.

Iodine azide Chemical compound

Iodine azide is an explosive inorganic compound, which in ordinary conditions is a yellow solid. Formally, it is an inter-pseudohalogen.


  1. 1 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
  2. 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.
  3. Wallingford, V. H.; Krüger, P. A. (1943). "5-Iodo-anthranilic Acid". Organic Syntheses .; Collective Volume, vol. 2, p. 349
  4. Padwa, A.; Blacklock, T.; Tremper, A. "3-Phenyl-2H-Azirine-2-carboxaldehyde". Organic Syntheses .; Collective Volume, vol. 6, p. 893