http___en.m.wikipedia.org_wiki_Iodoform.xml
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Йодоформ Йодоформ е химично съединение на йод, водород и въглерод, с формула CHI3. При нормални условия представлява бледожълто, кристално, летливо вещество с характерен остър мирис (който понякога е определян като "миризма на болница"). Използван е като антисептик при превръзването на рани в началото на 20 век, днес е заменен с по-добри антисептици. В органичната химия се използва като реактив за разпознаване на етилов алкохол (етанол). При нагряване на етанол в присъствие на йод и следващо алкализиране с натриева основа до обезцветяване, се наблюдава отделяне на бледо жълти кристали от йодоформ. Реакцията е качествена за доказването на етанол.
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Iodoform is the organoiodine compound with the formula CHI3. A pale yellow, crystalline, volatile substance, it has a penetrating odor (in older chemistry texts, the smell is sometimes referred to as the smell of hospitals) and, analogous to chloroform, sweetish taste. It is occasionally used as a disinfectant. It is also known as tri-iodomethane, and sometimes also referred to as carbon triiodide (which is not strictly correct, as this compound also contains hydrogen) or methyl triiodide (which is somewhat ambiguous as that name could also refer to the methylated triiodide ion, CH3I3). Synthesis and reactionsEdit Iodoform was first prepared by Georges Serrulas in 1822;[1] and at much the same time independently by John Thomas Cooper.[2] 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: (i) 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 secondary alcohols (methyl alcohols). 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, which is oxidized by mixture of sulfuric acid and iodine pentaoxide. 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 Angel's bonnets contain iodoform and show its characteristic odor. ApplicationsEdit The compound finds small scale use as a disinfectant.[3] 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, to prevent infection and facilitate removal of ear hair, along with zinc oxide and propanoic acid. See alsoEdit - Iodoform reaction - Group key for an unrelated cryptographic meaning of the term ReferencesEdit - Merck Index, 12 Edition, 5054. - ^ Georges-Simon Surellas, 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] (Metz, France: Antoine, 1822). On pages 17-20, Surellas produced iodoform by passing a mixture of iodine vapor and steam over red-hot coals. However, later, on pages 28-29, he produced iodoform by adding potassium metal to a solution of iodine in ethanol (which also contained some water). - ^ James, Frank A. J. L. "Cooper, John Thomas (1790–1854), chemist". Oxford Dictionary of National Biography. Oxford University Press. Retrieved 26 January 2012. - ^ Phyllis A. Lyday "Iodine and Iodine Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. External linksEdit - NIOSH Pocket Guide to Chemical Hazards 0343 - MSDS at JT Baker - A Method for the Specific Conversion of Iodoform to Carbon Dioxide - Article at 1911 Encyclopaedia Britannica - Preparation