Iodoform

Iodoform is the organoiodine compound with the formula 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 the smell of hospitals, where the compound is still commonly used) and, analogous to chloroform, sweetish taste. It is occasionally used as a disinfectant. It is also known as tri-iodomethane, carbon triiodide, and methyl triiodide.

Structure

The molecule adopts tetrahedral molecular geometry with C_3v symmetry.

Synthesis and reactions

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;^[5] and at much the same time independently by John Thomas Cooper.^[6] 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 (CH₃COR), acetaldehyde (CH₃CHO), ethanol (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 alcohols containing at least one methyl group in alpha-position.

Some reagents (e.g. hydrogen iodide) convert iodoform to diiodomethane. Also conversion to carbon dioxide is possible: 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 occurrence

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

Applications

The compound finds small scale use as a disinfectant.^[3]^[7] 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century it was used in medicine as a healing and antiseptic dressing for wounds and sores, although this use is now superseded by superior antiseptics. Adolf Hitler's mother, Klara Hitler, died of iodoform poisoning brought on by her treatment for breast cancer. It is the active ingredient in many ear powders for dogs and cats, along with zinc oxide and propanoic acid, which are used to prevent infection and facilitate removal of ear hair.

References

↑ Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 661. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4. The retained names ‘bromoform’ for HCBr₃, ‘chloroform’ for HCCl₃, and ‘iodoform’ for HCI₃ are acceptable in general nomenclature. Preferred IUPAC names are substitutive names.
1 2 3 4 5 6 7 Record in the GESTIS Substance Database of the IFA
1 2 Merck Index, 12 Edition, 5054
1 2 3 "NIOSH Pocket Guide to Chemical Hazards #0343". National Institute for Occupational Safety and Health (NIOSH).
↑ Surellas, Georges-Simon (1822), Notes sur l'Hydriodate de potasse et l'Acide hydriodique. -- Hydriodure de carbone; moyen d'obtenir, à l'instant, ce composé triple [Notes on the hydroiodide of potassium and on hydroiodic acid -- hydroiodide of carbon; means of obtaining instantly this compound of three elements] (in French), Metz, France: Antoine, pp. 17–20, 28–29
↑ James, Frank A. J. L. "Cooper, John Thomas (1790–1854), chemist". Oxford Dictionary of National Biography. Oxford University Press. Retrieved 26 January 2012.
↑ Lyday, Phyllis A. (2005), "Iodine and Iodine Compounds", Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim

External links

Medicated dressings (D09)

Ointment dressings with anti-infectives	Aluminium chlorohydrate Benzalkonium Benzododecinium Cetylpyridinium Chlorhexidine Clioquinol Framycetin Fusidic acid Iodoform Nitrofural Phenylmercuric nitrate Povidone-iodine Triclosan

Other	Soft paraffin dressings Zinc bandages

Halomethanes

Monosubstituted	CH₃F CH₃Cl CH₃Br CH₃I

Disubstituted	CH₂F₂ CH₂ClF CH₂BrF CH₂FI CH₂Cl₂ CH₂BrCl CH₂ClI CH₂Br₂ CH₂BrI CH₂I₂

Trisubstituted	CHF₃ CHClF₂ CHBrF₂ CHF₂I CHCl₂F CHBrClF CHClFI CHBr₂F CHBrFI CHFI₂ CHCl₃ CHBrCl₂ CHCl₂I CHBr₂Cl CHBrClI CHClI₂ CHBr₃ CHBr₂I CHBrI₂ CHI₃

Tetrasubstituted	CF₄ CClF₃ CBrF₃ CF₃I CCl₂F₂ CBrClF₂ CClF₂I CBr₂F₂ CBrF₂I CF₂I₂ CCl₃F CBrCl₂F CCl₂FI CBr₂ClF C*BrClFI CClFI₂ CBr₃F CBr₂FI CBrFI₂ CFI₃ CCl₄ CBrCl₃ CCl₃I CBr₂Cl₂ CBrCl₂I CCl₂I₂ CBr₃Cl CBr₂ClI CBrClI₂ CClI₃ CBr₄ CBr₃I CBr₂I₂ CBrI₃ CI₄

* Chiral compound.

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