Iodoform
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Iodoform (also known as triiodomethane) is the organoiodine compound with the chemical formula Template:Chem2. It is a pale yellow, crystalline, volatile substance, with 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.
NamingEdit
The name iodoform originates with the "formyle radical," an archaic term for the HC moiety,Template:Citation needed and is retained for historical consistency. A full, modern name is triiodomethane. Another possible name is "carbon hydride triiodide". The "hydride" in the latter is sometimes omitted,<ref name="pubchem"/> though the IUPAC recommends against doing so, as "carbon triiodide" could also mean Template:Chem2 (hexaiodoethane, a highly unstable compound).
StructureEdit
The molecule adopts a tetrahedral geometry with C3v symmetry.
Synthesis and reactionsEdit
The synthesis of iodoform was first described by Georges-Simon Serullas 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;<ref>Template:Citation</ref> and at much the same time independently by John Thomas Cooper.<ref name=ODNB>Template:Cite ODNB</ref> It is synthesized in the haloform reaction by the reaction of iodine and sodium hydroxide with any one of these four kinds of organic compounds: a methyl ketone (Template:Chem2), acetaldehyde (Template:Chem2), ethanol (Template:Chem2), and certain secondary alcohols (Template:Chem2, 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 alcohols containing at least one methyl group in alpha-position.
Some reagents (e.g. hydrogen iodide) convert iodoform to diiodomethane. Conversion to carbon dioxide is also possible.<ref>Template:Cite journal</ref> Iodoform reacts with aqueous silver nitrate to produce carbon monoxide. 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 occurrenceEdit
The angel's bonnet mushroom contains iodoform, and shows its characteristic odor.
ApplicationsEdit
The compound finds small-scale use as a disinfectant.<ref name=Merck/><ref>Template:Citation</ref> Around the beginning of the 20th century, it was used in medicine as a healing and antiseptic dressing for wounds and sores and, although this use is now largely superseded by superior antiseptics, it is still used in otolaryngology in the form of bismuth subnitrate iodoform paraffin paste (BIPP) as an antiseptic packing for cavities.<ref>Template:Cite journal</ref> It is the active ingredient in many ear powders for dogs and cats, along with zinc oxide and propionic acid, which are used to prevent infection and facilitate removal of ear hair.Template:Citation needed
See alsoEdit
ReferencesEdit
External linksEdit
Template:Medicated dressings Template:Halomethanes Template:Authority control