Iodoform, reaction

Note cautiously the characteristic odour of acetaldehyde which this solution possesses. Then with the solution carry out the following general tests for aldehydes described on p. 341 Test No. I (SchiflF s reagent). No. 3 (Action of sodium hydroxide). No. 4 (Reduction of ammoniacal silver nitrate). Finally perform the two special tests for acetaldehyde given on p. 344 (Nitroprusside test and the Iodoform reaction). 

For other types of compounds which give the iodoform reaction, see H. Booth and B. C. Saunders, Chem, and Industry 1950. 824. 

Hydrolysis of Acetoxime. Place about i g. of the recrystallised oxime in a small distilling-flask (50 ml.), add 10 ml. of dilute HjSO, and heat gently until about half the solution has distilled over. Test [a] the aqueous distillate for acetone by the iodoform reaction (p.346), b) the residual solution in the distilling-flask for hydroxylamine by... 

Iodoform Reaction. To 0 5 ml. of ethanol add 3 ml. of 10% KI solution and 10 ml. of NaOCl solution. Warm gently fine yellow crystals of CHI3 separate. Isopropanol gives CHIj in the cold. Pure methanol and the other alcohols in this section go not give the reaction. 

Gives some of the tests for acetaldehyde, but more feebly e.g., it restores the colour to SchifF s reagent, gives a yellow resin with NaOH, and responds to the nitroprusside test. With ammoniacal AgN03, it gives a silver minor only after 2 -3 minutes warming. It does not give the iodoform reaction. 

Ketones containing the CH3CO— group give the iodoform reaction. (For other compounds which give this test, see p- 91.)... 

If the compound to be tested is insoluble in water, it should be brought into solution by the addition of a little dioxan. Alcohols and some methyl ketones frequently react slowly in such cases it is advisable to employ a large excess (4-5 fold) of the relatively unstable reagent (3NaOI -> NaI03 -f- 2NaI). Quinones and hydroquinones also give the iodoform reaction. 

In current industrial practice gas chromatographic analysis (glc) is used for quahty control. The impurities, mainly a small amount of water (by Kad-Fischer) and some organic trace constituents (by glc), are deterrnined quantitatively, and the balance to 100% is taken as the acetone content. Compliance to specified ranges of individual impurities can also be assured by this analysis. The gas chromatographic method is accurately correlated to any other tests specified for the assay of acetone in the product. Contract specification tests are performed on product to be shipped. Typical wet methods for the deterrnination of acetone are acidimetry (49), titration of the Hberated hydrochloric acid after treating the acetone with hydroxylamine hydrochloride and iodimetry (50), titrating the excess of iodine after treating the acetone with iodine and base (iodoform reaction). 

This still retains the initial ethylenic linkage and can be hydrogenated to heliotridane (II). The hydrochloride in water is oxidised by ozone to 2-acetylpyrrolidinoacetic acid (XIV) hydrochloride, m.p. 180-1°, — 4-4° (MeOH). In this the presenee of the. CO. CHj group is shown by a positive iodoform reaction and the formation of a 2 4-dinitro-... 

Monocrotaline on alkaline hydrolysis yields retronecine and monocrotic acid, CjHijOg, b.p. 145-6°/18 mm., [a]p 0°, which forms a p-bromo-phenacylester, m.p. 78°,and a methyl ester, b.p. 94-6°/18 mm., characterised by a 2 4-dinitrophenylhydrazone, m.p. 95-6° see below). The acid gives the iodoform reaction and is oxidised by sodium hypobromite to a mixture of dl- and mcso-aa -dimethylsuccinic acids (I). These and other reactions show that monocrotic acid is a -dimethyllaevulic acid (II) and this has been eonfirmed by comparison with a synthetic specimen of the acid. The methyl ester of the synthetie acid forms a mixture of 2 4-dinitrophenylhydrazones, m.p. 108-9° and 121-2°, into which the analogous produet, m.p. 95-6°, first made from methyl monocrotate see above), has also been separated. 

Commercial methyl alcohol is obtained by purifying wood spirit. It often contains a little acetone, which may be detected by the iodoform reaction (see p. 50). It may, if necessary, be purified by boiling it, using an upright condenser, with 3—4 percent, of solid... 

Reactions.—i. Acetone gives the iodoform reaction like ethyl alcohol (p. 50). 2. Dissolve a few crystals of /-bromophenyl-... 

Alcohol can be detected h,v dislilJicig a few c.c. of Ihc sample with water, aud testing the distillate by the usual iodoform reaction. It the sample bo wHshed with warm waler in a separator, and the retractivu index of the washed otto l>c examined, it will be found to he higher than that ol the original otto. II this exoes.s be more (ban fl-Ofll i is almost certainly due to alcohol. 

In the iodoform reaction, a triiodomethyl ketone reacts with aqueous NaOH to yield a carboxylate ion and iodoform (triiodomethane). Propose a mechanism for this reaction. 

Investigational new drug (IND), 165 lodination (aromatic), 551 Iodoform reaction. 854-855 lodomethane, bond length of, 335 bond strength of, 335 dipole moment of. 335... 

Iodoform reaction with sodium hypoiodite is also used for detection of CHgCO group or CH3CH(OH) group which produces CH3CO group on oxidation. 

This reaction works equally well with chlorine or iodine and is known as the chloroform or iodoform reactions in these cases after the names of the products. 

The cleavage reaction does not occur unless there are three halogens on the carbon, so only methyl groups are removed in this manner. The reaction with 12 (iodoform reaction) has been used as a test for methyl ketones. The formation of iodoform (CHI3),... 

Iodine is an oxidizing agent, and an alcohol can give a positive iodoform test if it oxidizes to a methyl ketone. The iodoform reaction can convert such an alcohol to a carboxylic acid with one less carbon atom. 

The conversion of a methyl ketone to a carboxylate ion and a haloform (CHX3) by treatment with a halogen and base. The iodoform reaction uses iodine to give a precipitate of solid iodoform, (p. 1056)... 

This reaction is often called the iodoform reaction. Iodoform was an old name for tri-iodomethane, just as chloroform is still used for trichloromethane. It is one of the rare cases where nucleophilic substitution at a carbonyl group results in the cleavage of a C-C single bond. 

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