Ketones, methyl qualitative test

Hypoiodites are used for qualitative tests for methyl ketones (Lieben test). For this purpose, a compound to be tested is stirred with an aqueous solution of sodium hydroxide (80 mol/mol of methyl ketone). Iodine (4.5 mol of 12) is added portionwise with stirring, and the mixture is set aside for 20 min at 25 °C before acidification. In the presence of a methyl keto group, a yellow heavy precipitate of iodoform settles at the bottom of the test tube. Iodoform can be identified easily not only by its characteristic smell but also by its melting point (120-123 °C) [1173], This test applies not only to methyl ketones but to any compound that can be converted in the reaction medium into a species containing the COCH3 group, for example, isopropyl or ethyl alcohol. 

The fragmentation reaction that is most often first encountered is the iodoform reaction. This is because it forms the basis of a very easy qualitative test for the presence of a methyl ketone, or alternatively the CH3CH(OH)- grouping. If a methyl ketone is treated with iodine and sodium... 

A student is trying to prove the identity of a compound that she synthesized. She knows that the compound is a methyl ketone. Which of the following qualitative tests can be used to prove the identity of the synthesized compound as a methyl ketone ... 

Rapid, simple, qualitative methods suitable for detemiining the presence of benzene in the workplace or surroundings have been utilized since the 1930s. Many early tests offered methods for detection of aromatics but were not specific for benzene. A straightforward test allowing selective detection of benzene involves nitration of a sample to w-dinitrobenzene and reaction of the resultant ether extract with an ethanolic solution of sodium hydroxide and methyl ethyl ketone (2-butanone), followed by the addition of acetic acid to eliminate interferences from toluene and xylenes. Benzene imparts a persistent red color to the solution (87). The method is claimed to be sensitive to concentrations as low as 0.27 ppm benzene from 10 mT, air samples. 

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... 

In the old days, before spectroscopic analysis became routine, this reaction, when carried out with iodine (X = I), was used as a qualitative visual test for methyl ketones because the iodoform (CHI3) produced is easily recognizable as a pale yellow solid. Nowadays, the reaction is used mainly as a means of shortening the carbon chain of a methyl ketone. The mechanism involves repeated generation of a terminal enolate from the methyl ketone and its reaction with HOX, a weak acid and the putative halogenating agent under the reaction conditions ... 

Since solubility tests are of qualitative character only, certain compounds near the border line must be listed in more than one place to avoid error. For example, several of the compounds listed on page 189 will be reported normally insoluble in water according to the standards set in Chapter TII. Such compounds, therefore, will be found also in the water-insoluble groups, e.g.. Methyl isobutyrate, ethyl propionate, and n-propyl acetate are listed in V, 5 methyl propyl ketone and diethyl ketone in V, 3, etc. 

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