Haloform test

Problem 13.48 Methyl ketones gives the haloform test ... 

Ij can also oxidize 1° and 2° alcohols to carbonyl compounds. Which butyl alcohols give a positive haloform test ... 

Color reactions Boric acid (hydroxyquinones). Dimethylaminobenzaldehyde (pyrroles). Ferric chloride (enols, phenols). Haloform test. Phenylhydrazine (Porter-Silber reaction). Sulfoacetic acid (Liebermann-Burchard test). Tetranitromethane (unsaturation). Condensation catalysts /3-Alanine. Ammonium acetate (formate). Ammonium nitrate. Benzyltrimethylammonium chloride. Boric acid. Boron trilluoride. Calcium hydride. Cesium fluoride. Glycine. Ion-exchange resins. Lead oxide. Lithium amide. Mercuric cyanide. 3-Methyl-l-ethyl-2-phosphoiene-l-oxlde. 3-Methyl-1-phenyi-3-phoipholene-1-oxide. Oxalic acid. Perchloric acid. Piperidine. Potaiaium r-butoxIde. Potassium fluoride. Potassium... 

Haloform test, 425 Halohydrination, 800 Halomycin, 265 Haplophyline, 855 Hecogenin, 152 tosylhydrazone, 1186-1187 Helium, 409... 

Haloform test. A modification of a test devised by Fujiwara permits detection of fluoroform, chloroform, bromoform, or iodoform or of any precursor of a haloform or of a dihalocarbene. A few drops of a mixture suspected of containing a haloform or a precursor is added to a mixture of 3 ml. of 10% sodium hydroxide and 2 ml. of pyridine. If the mixture turns pink to bright blue-red within one or two minutes of vigorous shaking at room temperature, a haloform is present. If the color change occurs not at room temperature but when the solution is heated on the steam bath for one minute, a precursor of a haloform or a dichlorocarbene is indicated. The intensity of the color is proportional to the concentration of haloform or of precursor. 

The iodoform test is sometimes called the hypoiodite test because sodium hypoiodite is formed according to Equation 25.21. In more general terms, the reactions just described can be called the haloform test or the sodium hypohalite test... 

The haloform reaction using iodine was once used as an analytical test in which the formation of a yellow precipitate of iodoform was taken as evidence that a substance... 

Besides its synthetic importance, the haloform reaction is also used to test for the presence of a methylketone function or a methylcarbinol function in a molecule. Such compounds will upon treatment with iodine and an alkali... 

When the halogen is iodine, the haloform product (iodoform) is a solid that separates out as a yellow precipitate. This iodoform test identifies methyl ketones, which halo-genate three times, then lose CI3 to give iodoform. 

The haloform reaction (Problem 22.23d) is an alpha-substitution reaction in which a methyl ketone is trihalogenated at the alpha position, and the trihalomethyl group is displaced by -OH. It is a test for methyl ketones. 

Iodoform test (Section 23.7B) A test for the presence of methyl ketones, indicated by the formation of the yellow precipitate, CHI3, via the haloform reaction. 

This sensitive test permits use of the readily available sodium hypochlorite in place of sodium hypoiodite for recognition of methyl carbonyl or methylcarbinol structures. It is useful also when detection of a haloform by infrared spectroscopy or gas-liquid chromatography is unsatisfactory, as may happen in certain reactions in which haloform-type cleavage occurs to a slight extent. ... 

The haloform reaction, using iodine, was once used as an analytical test in which the formation of a yellow precipitate of iodoform was taken as evidence that a substance was a methyl ketone. This application has been superseded by spectroscopic methods of structure determination. Interest in the haloform reaction has returned with the realization that chloroform and bromoform occur naturally and are biosynthesized by an analogous process. (See the boxed essay The Haloform Reaction and the Biosynthesis of Trihalomethanes. )... 

The reaction of methyl ketones with excess hydroxide and chlorine, bromine or iodine leads to the formation of a carboxylic acid together with CHX3 in a haloform reaction. The use of iodine gives CHI3 (iodoform), which is the basis of a functional group test for methyl ketones. 

An important variation is that compounds such as methyl carbinols also undergo the Haloform reaction since they are typically oxidized to the corresponding methyl ketone under the reaction conditions. This reaction is particularly well known to undergraduate organic chemistry students as the "Iodoform Test" in qualitative organic... 

The two possible products can be distinguished by an iodoform test. A haloform reaction is the base-catalyzed substitution of all three methyl-hydrogens by three halogens, Since 2-methyl-l-phenyl-l,3-butanedione contains an acetyl methyl group, it will readily undergo an iodoform reaction, while 1-phenyl-l,3-pentanedione will not. 

Norwood et al. (1980) chlorinated a considerable number of phenolic acids of both benzoic and cinnamic acid types and looked for haloform production. Concentrations were from 0.5-6 mM and approximately a twofold excess of chlorine was added. For most of the acids tested, except those with 1,3-dihydroxy (resorcinol-type) substituents, chloroform yields were low (0-4 7o) except in the case of 3-methoxy-4-hydroxycinnamic acid (ferulic acid, 10), where about an 11% yield was... 

Treatment of [3] with acetylchloride in dichloroethane m the presence of AICI3 (Friedel-Craft s acylation) gives tetrahydrotetramethylacetylnaphthalene [4], which can be converted to tetrahydrotetramethylnaphthoic acid [5] by treatment with high-test bleaching powder (haloform reaction) (4,6). 

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