Iodoform (also known as triiodomethane and, inaccurately, as carbon triiodide) is the

organoiodine compound Organoiodine compounds are organic compounds that contain one or more carbon–iodine bonds. They occur widely in organic chemistry, but are relatively rare in nature. The thyroxine hormones are organoiodine compounds that are required for he ...

with the

chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbol ...

C H I₃. A pale yellow, crystalline, volatile substance, it has a penetrating and distinctive odor (in older chemistry texts, the smell is sometimes referred to as that of hospitals, where the compound is still commonly used) and, analogous to chloroform, sweetish taste. It is occasionally used as a disinfectant.

Structure

The molecule adopts

tetrahedral molecular geometry In a tetrahedral molecular geometry, a central atom is located at the center with four substituents that are located at the corners of a tetrahedron. The bond angles are arccosine, cos−1(−) = 109.4712206...° ≈ 109.5° when all four substit ...

with C_3v symmetry.

Synthesis and reactions

The synthesis of iodoform was first described by

Georges-Simon Serullas Georges-Simon Serullas (2 November 1774 in Poncin – 25 May 1832 in Paris) was a professor of pharmacy notable for being the first to publish a work on Iodoform, an early antiseptic and disinfectant. Biography He was a professor and head pharm ...

in 1822, by reactions of iodine vapour with steam over red-hot coals, and also by reaction of potassium with ethanolic iodine in the presence of water; and at much the same time independently by

John Thomas Cooper John Thomas Cooper (1790–1854) was an English chemist notable as a lecturer, chemical supplier and chemical analyst, at a time when interest was burgeoning in chemistry as a discipline of study and application. Biography Cooper was born in Gre ...

. It is synthesized in the

haloform reaction In chemistry, the haloform reaction is a chemical reaction in which a haloform (, where X is a halogen The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), ...

by the reaction of iodine and sodium hydroxide with any one of these four kinds of organic compounds: a methyl ketone (CH₃COR), acetaldehyde (CH₃CHO),

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

(CH₃CH₂OH), and certain secondary alcohols (CH₃CHROH, where R is an alkyl or aryl group). : The reaction of iodine and base with methyl ketones is so reliable that the iodoform test (the appearance of a yellow precipitate) is used to probe the presence of a methyl ketone. This is also the case when testing for specific

secondary alcohol In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which is ...

s containing at least one methyl group in alpha-position. Some reagents (e.g. hydrogen iodide) convert iodoform to

diiodomethane Diiodomethane or methylene iodide, commonly abbreviated "MI", is an organoiodine compound. Diiodomethane is a colorless liquid; however, it decomposes upon exposure to light liberating iodine, which colours samples brownish. It is slightly solub ...

. Also conversion to

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

is possible: Iodoform reacts with aqueous

silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar causti ...

to produce

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

. When treated with powdered elemental silver the iodoform is reduced, producing acetylene. Upon heating iodoform decomposes to produce diatomic iodine, hydrogen iodide gas, and carbon.

Natural occurrence

The angel's bonnet mushroom contains iodoform, and shows its characteristic odor.

Applications

The compound finds small-scale use as a disinfectant. Around the beginning of the 20th century, it was used in medicine as a healing and antiseptic dressing for wounds and sores, although this use is now superseded by superior

antiseptic An antiseptic (from Greek ἀντί ''anti'', "against" and σηπτικός ''sēptikos'', "putrefactive") is an antimicrobial substance or compound that is applied to living tissue/skin to reduce the possibility of infection, sepsis, or putre ...

s. It is the active ingredient in many ear powders for

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...

s and

cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...

s, along with

zinc oxide Zinc oxide is an inorganic compound with the formula . It is a white powder that is insoluble in water. ZnO is used as an additive in numerous materials and products including cosmetics, food supplements, rubbers, plastics, ceramics, glass, cement ...

and propionic acid, which are used to prevent infection and facilitate removal of ear hair.

References

External links

*
MSDS at JT BakerA Method for the Specific Conversion of Iodoform to Carbon DioxidePreparation
* {{Use dmy dates, date=April 2017 Iodoalkanes Halomethanes Antiseptics Iodine-containing natural products