Sodium hypoiodite

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

The synthesis of the four monocarboxylic acids of dibenzothiophene has been recorded in the previous review. However, several modified preparations have since been described. Ethyl 1-dibenzothiophene-carboxylate has been synthesized from 2-allylbenzo[6]thiophene (Section IV,B, 1) hydrolysis afforded the 1-acid (57% overall). In a similar manner, 3-methyl-1-dibenzothiophenecarboxylic acid was obtained from the appropriately substituted allyl compound. This method is now the preferred way of introducing a carbon-containing substituent into the 1-position of dibenzothiophene. 2-Dibenzothiophenecarboxylic acid has been prepared by oxidation of the corresponding aldehyde or by sodium hypoiodite oxidation of the corresponding acetyl compound. Reaction of 2-acetyldibenzothiophene with anhydrous pyridine and iodine yields the acetyl pyridinium salt (132) (92%), hydrolysis of which yields the 2-acid (85%). The same sequence has been carried out on 2-acetyldibenzothiophene 5,5-dioxide. The most efficient method of preparing the 2-acid is via carbonation of 2-lithio-... 

For years the iodoform test was a laboratory method for the identification of a methyl ketone (a ketone where one of the R groups is a methyl group). A positive test produced the compound iodoform. Iodoform, CHI3, is a yellow precipitate with a characteristic odor. The oxidation utilizes sodium hypoiodite, which is generated in situ by the reaction of iodine with sodium hydroxide. Figure 10-35 shows an example of the iodoform test. 

Prepared by reaction (I) of iodine and mercuric oxide (see also Mercury) suspension in water, mercuric iodide being simultaneously formed. (2) of sodium hypoiodite and an acid, excess acid yielding iodine. 

The structure of 138 was elucidated, shortly after its isolation, in extensive contributions by many groups. Several important discoveries relating to its constitution were reported in 1933, the same year in which the first successful synthesis was described (see Refs. 274, 324). Thus, the group at the University of Birmingham335 found that the primary oxidation product of 138, the 2,3-diulosono-lactone 148 (dehydroascorbic acid), could be quantitatively oxidized by sodium hypoiodite to generate oxalic acid and L-threonic acid (Scheme 16), which was identified as the crystalline tri-O-methyl-L-threonamide. These results established the stereochemical relationship between 138 and L-gulonic (and L-idonic) acid. The work that provided support for the structure of L-ascorbic acid has been summarized in several reviews.274,336... 

Acetone (0.2%) is removed from methanol by treating it with sodium hypoiodite. Iodine (25 g) is dissolved in 1 1 of methanol and the solution slowly poured, with constant stirring, into 500 ml of 1 N sodium hydroxide solution. The iodoform is precipitated upon the addition of 150 ml of water. After standing overnight, the solution is filtered and the filtrate boiled under reflux until the smell of iodoform disappears. A single fractional distillation produces 800 ml of acetone-free methanol. 

Sodium hypoiodite, NaOI.—The hypoiodite has never been isolated, but is formed in dilute aqueous solution by the interaction of sodium hydroxide and iodine, and to a small extent by the electrolysis of an alkaline solution of sodium iodide. The substance is extremely unstable, reduction to iodide and oxidation to iodate taking place simultaneously.5... 

Pfitzner and Moffatt339 characterized 3 -0-acetylthymidine-5 -alde-hyde by oxidation with alkaline sodium hypoiodite to the corresponding acid which, upon alkaline hydrolysis, gave 120. 

Kline and Acree studied the hypoiodite oxidation extensively. The alkali and iodine were both added in small portions throughout the reaction. In this manner the concentration of sugar relative to the sodium hypoiodite was kept at a level favorable to the sugar oxidation (reaction 14). At the end of the reaction, the formation of iodate increased rapidly (reaction 15), taking precedence over the oxidation of ketoses and non-reducing sugars. 

A definite method for the determination of D-fructose in the presence of aldoses was worked out by Kruisheer 98.3% of theory was found. The aldoses were oxidized with sodium hypoiodite, after which the excess iodine was titrated with sodium sulfite. Thiosulfate could not be used here, since the subsequent determination of D-fructose was carried out with an alkaline copper solution by the Luff-Schoorl method. 

The above methods are so designed that the oxidation of ketoses by sodium hypoiodite is restricted to a minimum. Bailey and Hopkins studied the conditions under which ketoses would be oxidized. The reaction rate increased with the temperature, and the extent of the reaction, which was studied over the temperature range of 1 to 35 , went through a minimum at 15°. An excess of alkali in the 17-37 range apparently caused enolization of the D-fructose and increased the extent of the oxidation. When the alkali was added progressively in small amounts, this effect was increased 4-5 times and was independent of the D-fructose concentration. Oxalic acid was isolated and the presence of D-erythronic acid was assumed. 

An exception to the normal behavior of ketoses with alkaline sodium hypoiodite has been noted in the case of D-xyloketose. This keto-pentose reduces very strongly and could not be distinguished in a mixture with D-xylose by the Willstatter-Schudel method. 

In their speed of reaction with the halogens, in acid or in alkaline solutions, the simple sugars may be divided into two main classes, the aldoses and the ketoses. The oxidation of the former is very rapid compared with that of the latter. Kiliani showed that when D-glucose and D-fructose were each treated with an equal weight of bromine in water, the ketose required 350-500 hours for completion of the oxidation, in contrast to two to three hours for the aldose. The same difference exists in buffered solutions Honig and Ruzicka found that the rates were two hours and five minutes, respectively. In alkaline solution under controlled conditions, the aldoses can be quantitatively oxidized with sodium hypoiodite in the presence of D-fructose or L-sorbose without appreciable attack on the ketoses. Ochi reported a similar but less clear-cut difference with calcium hypochlorite as the oxidant. Chlorous acid attacks only the aldoses, leaving the ketoses unaltered. The same effect was noted with the keto acids Kiliani reported that 2-keto-L-rhamnonic acid was stable to the action of bromine water. A little preliminary work has been done with iodic acid by Williams and Woods who found that D-fructose was oxidized more rapidly than the aldoses. No confirmation of this work has appeared. 

Whether or not an alcohol contains one particular structural unit is shown by the iodoform test. The alcohol is treated with iodine and sodium hydroxide (sodium hypoiodite, NaOI) an alcohol of the structure... 

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. ... 

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