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. Detection of ketones.
The chemistry of the triiodomethane (iodoform) reaction. What the triiodomethane (iodoform) reaction shows. A positive result-the pale yellow precipitate of triiodomethane (iodoform) - is given by an alcohol containing the grouping: R can be a hydrogen atom or a hydrocarbon group (for example, an alkyl group). Summary of the reactions during the triiodomethane (iodoform) reaction We will take the reagents as being iodine and sodium hydroxide solution. This is being given as a flow scheme rather than full equations. Fig.2. Iodoform reaction. The iodoform reaction may be analytically used for the detection of methyl ketones. For this purpose, the sample is treated with hypoiodite as a source of iodine in basic solution.  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. 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. This page looks at how the triiodomethane (iodoform) reaction can be used to identify the presence of a CH 3 CO group in aldehydes and ketones. Note: This reaction can also be used in testing for the CH 3 CH(OH) group in alcohols. You will find a link to this at the bottom of the page. The chemistry of the triiodomethane (iodoform) reaction. What the triiodomethane (iodoform) reaction shows. A positive result-the pale yellow precipitate of triiodomethane (iodoform) - is given by an aldehyde or ketone containing the grouping: Iodoform is the organoiodine compound with the formula C H I 3. 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. Iodoform Reaction. The iodoform test indicates the presence of an aldehyde or ketone in which one of the groups directly attached to the carbonyl carbon is a methyl group. Such a ketone is called a methyl ketone. In the iodoform test, the unknown is allowed to react with a mixture of iodine and base. Hydrogens alpha to a carbonyl group are acidic and will react with base to form the anion, which then reacts with iodine to form an alpha-iodo ketone. 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: CH 3 COR, acetaldehyde (CH 3 CHO), ethanol (CH 3 CH 2 OH), and certain secondary alcohols (CH 3 CHROH, where R is an alkyl or aryl group). 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. The iodoform test or iodoform reaction is a qualitative chemical test for the detection of ketones and aldehydes carrying an alpha methyl group. The reagents are iodine and sodium hydroxide. Only methyl ketones, or alcohols with the feature: CH3CH(OH)-R may undergo this reaction. Report Abuse. -The iodoform test or reaction is a chemical reaction where iodoform (CHI3) is produced by the multiple halogenation of a methyl ketone (a molecule containing the R-CO-CH3 group) in the presence of a base. R may be H, alkyl or aryl. The reaction can be used to produce CHCl3, CHBr3 or CHI3 This page looks at how the triiodomethane (iodoform) reaction can be used to identify the presence of a CH 3 CH(OH) group in alcohols. Note: This reaction can also be used in testing for the CH 3 CO group in aldehydes and ketones. Summary of the reactions during the triiodomethane (iodoform) reaction We will take the reagents as being iodine and sodium hydroxide solution. This is being given as a flow scheme rather than full equations.
http://chemguide.co.uk/organicprops/alcohols/iodoform.html http://www.chemgapedia.de/vsengine/vlu/vsc/en/ch/12/oc/vlu_organik/keto_enol/racem_halo_haloform_alkylierung.vlu/Page/vsc/en/ch/12/oc/keto_enol/halo/haloform.vscml.html https://en.wikipedia.org/wiki/Iodoform http://www.chemguide.co.uk/organicprops/carbonyls/iodoform.html https://en.wikipedia.org/wiki/Iodoform http://www.chem.umass.edu/~samal/269/aak.pdf https://en.wikipedia.org/wiki/Iodoform https://in.answers.yahoo.com/question/index?qid=20071023102326AAsfaJw http://chemguide.co.uk/organicprops/alcohols/iodoform.html
what is the purpose of iodoform reaction