Iodine monochloride is an

interhalogen compound In chemistry, an interhalogen compound is a molecule which contains two or more different halogen atoms ( fluorine, chlorine, bromine, iodine, or astatine) and no atoms of elements from any other group. Most interhalogen compounds known are b ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

. It is a red-brown chemical compound that melts near

room temperature Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a person when they are wearing typical indoor clothing. Human comfort can extend beyond this range depending on ...

. Because of the difference in the electronegativity of

iodine 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 , and boils to a vi ...

and chlorine, this molecule is highly

polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates * Polar climate, the c ...

and behaves as a source of I⁺.

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 Iodine trichloride is an interhalogen compound of iodine and chlorine. It is bright yellow but upon time and exposure to light it turns red due to the presence of elemental iodine. In the solid state is present as a planar dimer I2Cl6, with two br ...

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.Brisbois, R. G.; Wanke, R. A.; Stubbs, K. A.; Stick, R. V. "Iodine Monochloride" Encyclopedia of Reagents for Organic Synthesis, 2004 John Wiley & Sons. 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 HCL may refer to: Science and medicine * Hairy cell leukemia, an uncommon and slowly progressing B cell leukemia * Harvard Cyclotron Laboratory, from 1961 to 2002, a proton accelerator used for research and development * Hollow-cathode lamp, a spe ...

but reacts with pure water to form HCl, iodine, and

iodic acid Iodic acid is a white water-soluble solid with the chemical formula . Its robustness contrasts with the instability of chloric acid and bromic acid. Iodic acid features iodine in the oxidation state +5 and is one of the most stable oxo-acids of ...

: : + O₂ : + O₂ : ICl is a useful

reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

. It is used as a source of

electrophilic In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carri ...

iodine in the synthesis of certain aromatic iodides. It also cleaves C–Si bonds. ICl will also add to the double bond in alkenes to give chloro-iodo

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which ...

s. :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 A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any sp ...

that forms 1:1

adducts An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...

with Lewis bases such as

dimethylacetamide Dimethylacetamide (DMAc or DMA) is the organic compound with the formula CH3C(O)N(CH3)2. This colorless, water-miscible, high-boiling liquid is commonly used as a polar solvent in organic synthesis. DMA is miscible with most other solvents, altho ...

and benzene.

References

{{Chlorides Iodine compounds Chlorides Interhalogen compounds Oxidizing agents