With hypohalites

Since aldehydes are notoriously polymerizable and difficult to manipulate, the products of periodate oxidation are oftentimes further oxidized, with hypohalite, to carboxylic acids, or are reduced to the corresponding alcohols. Oxidation has been more usually employed than reduction, since acids frequently form crystalline salts and other conveniently prepared derivatives. A process of oxidation of these aldehydic products by hypo-bromite, in the presence of barium carbonate or strontium carbonate, was developed and used extensively by Hudson and his coworkers.107 110 194-199,90s Their method can best be illustrated by an example the further oxidation of the dialdehyde, VI, shown previously (see p. 16) to be obtained by the oxidation of the methyl a-D-aldohexopyranosides. The isolation of... 

Upon treatment of primary amides with hypohalites, primary amines with one less carbon are obtained via the intermediacy of isocyanate. Also know as the Hofmann degradation reaction. 

General methods of preparation for alkenyl and alkynyl halides are listed in Table 14-5. By the alkynyl halides we mean 1-halo-alkynes. One interesting method by which they may be prepared employs 1-alkynes with hypohalites ... 

Acylureas react with hypohalite in alkali to yield A-haloureas which are converted into oxadiazolinones (94). Rearrangement of the N-halourea to an isocyanate presumably occurs during the reaction (Scheme 17). 

Reaction of hydrogen peroxide with hypohalites has been examined in acidic solutions and, very much less completely, under alkaline conditions. The reaction of hydrogen peroxide and chlorine in hydrochloric acid proceeds according to equation (16), with a rate law (17)... 

An interesting reaction, giving an acid with the same number of carbon atoms, takes place when some ketones (having a and a hydrogens) are stirred for 10-60 min at 25-80 °C with powdered potassium hydroxide, carbon tetrachloride, water, and ten-butyl alcohol [954] (equation 418). Ketones with a hydrogens but not a hydrogens give the same product as that obtained by oxidation with hypohalites [954. ... 

Aryl methyl ketones give generally high yields of acids on treatment with hypohalites [6SS, 696,698, 736. The reaction of 1,3,5-triacetylbenzene and sodium hypochlorite results in a 94% yield of trimesic acid [655], and that of methyl p-naphthyl ketone and sodium hypochlorite gives an 87-88% yield of p-naphthoic acid [695]. 4-Acetyl-4 -methoxybiphenyl is converted... 

It is known from Houben-Weyl, Methoden der organischen Chemie, volume 8, pages 415-416, that carboxylic acids can be manufactured by oxidation of methyl ketones with hypohalites in an aqueous medium. The publication recommends dispersing the ketone by means of oxidation-resistant emulsifiers or carrying out the reaction in the presence of dioxane all the examples were carried out in this way. In most cases the reaction only takes place satisfactorily with hypobromite solutions, which are more expensive and less stable than hypochlorite solutions. For this reason alone, industrial utilization of the reaction is confined to special reactions with aromatic ketones. 

The anion of this acid results from the oxidation of red phosphorus with hypohalites in alkaline solution ... 

Diazirine was used as the carbene precursor in an experiment to make diazomethane from methylene and nitrogen in the gas phase. As shown by means of labeled nitrogen, there was 4% diazomethane formation. During the past 10 years thermal as well as photochemical decomposition of 3-chloro- and 3-bromodiazirine has been investigated in detail. Compounds 175 and 176 as well as analogous compounds are easily obtained by reaction of amidines with hypohalites according to Graham. ... 

Several prespotter formulations are disclosed in the patent literature. Acidic compositions that contain a mixture of nonionic surfactants and hydrotropes [163], thickened alkaline products with hypohalite bleaches [164,165], and enzyme-containing formulas [ 166] have all been developed for use as prespotters. Although... 

Conversion of primary carboxylic amides to primary amines with one fewer carbon atom upon treatment with hypohalites or hydroxide via the intermediate isocyanate ... 

The mechanism by which hypohalites oxidize alcohols probably involves initial formation of an alkyl hypohalite (Eq. 16.16). This product arises from reaction of the alcohol with the hypohalous acid that is in equilibrium with hypohalite ion in aqueous medium (Eq. 16.15). Base-promoted E2 elimination of the elements of H-X from the alkyl hypochlorite leads directly to either an aldehyde or ketone. The advantage of using hypohalite as an oxidant is immediately obvious upon examining Equation 16.16. The inorganic by-product derived from the oxidant is a halide salt that can be safely flushed down the drain. Reactions that do not produce toxic by-products are environmentally friendly and are now commonly referred to as "Green Chemistry." (See the Historical Highlight at the end of this chapter.)... 

Oxidation with Hypohalites in Alkaline Solutions. In alkaline solution the halogens exist as hypohalous acid and hypohalite ions. The oxidation is likely to be more drastic than for the free halogens. Thus, whereas free iodine will not act as an oxidant, hypoiodite is a powerful oxidizing agent. Hypobromite and hypochlorite particularly are likely to produce oxidation of primary and secondary alcoholic groups and cause cleavage of carbon-carbon bonds. As noted above, the processes are complicated by the tendency of hypohalite to be converted to halate ions. 

The Hofmann rearrangement with hypohalites, the Schmidt reaction, and the Curtius reaction are three closely related methods of preparing amines. While all of them have been used extensively, since they afford a means of converting carboxylic acid derivatives to amines with one less carbon atom, they all are considered somewhat hazardous reactions. Of the three, probably the Hofmann rearrangement is... 

Haloform reactions are generally performed with halogens in the presence of hydroxide [251] or directly with hypohalites [252]. Alternative methods affording carboxylic acids from methyl ketones (or other enolizable substrates) include the aerobic oxidation in the presence of a catalytic amount of dinitrobenzene [253] with a base in a dipolar aprotic solvent such as DMF [254] or HMPT (hexamethylphospho-ric triamide) [255, 256] and the use of stoichiometric quantities of hypervalent iodide derivatives [95, 257] or nitrosylpentacyanoferrate [258]. Furthermore, metal catalysts can be used, and systems such as tert-butyl hydroperoxide in the presence of rhenium oxide [259], oxygen in combination with a copper complex [260], heteropolyacids [261] and Mn"/Co" systems [262] were found to be applicable. Finally, aryl ketones are selectively oxidized to aliphatic carboxylic acids by treatment with periodate [81] in the presence of ruthenium trichloride [263]. 

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