Carboxylic reactions with hypochlorite

Methyl ketones are degraded to the next lower carboxylic acid by reaction with hypochlorite or hypobromite ions. The initial step in these reactions involves base-catalyzed halogenation. The a-haloketones are more reactive than their precursors, and rapid halogenation to the trihalo compound results. Trihalomethyl ketones are susceptible to alkaline cleavage because of the inductive stabilization provided by the halogen atoms. 

We have found that carboxylic acids are obtained advantageously from methyl ketones by reaction with hypochlorites in an aqueous medium... 

Nickel peroxide is a solid, insoluble oxidant prepared by reaction of nickel (II) salts with hypochlorite or ozone in aqueous alkaline solution. This reagent when used in nonpolar medium is similar to, but more reactive than, activated manganese dioxide in selectively oxidizing allylic or acetylenic alcohols. It also reacts rapidly with amines, phenols, hydrazones and sulfides so that selective oxidation of allylic alcohols in the presence of these functionalities may not be possible. In basic media the oxidizing power of nickel peroxide is increased and saturated primary alcohols can be oxidized directly to carboxylic acids. In the presence of ammonia at —20°, primary allylic alcohols give amides while at elevated temperatures nitriles are formed. At elevated temperatures efficient cleavage of a-glycols, a-ketols... 

The reaction can also be effected with hypochlorite ion, and this constitutes a useful method for converting methyl ketones to carboxylic acids. 

Nickel(lll) oxide, prepared from a nickel(ii) salt and sodium hypochlorite, is used for the oxidation of alkanols in aqueous alkali [46]. Residual nickel(Ii) oxide can be re-activated by reaction with sodium hypochlorite. Nickel oxides have also long been used in the manufacture of the positive pole in the Edison nickel-iron rechargeable battery, now largely superseded by die lead-acid accumulator, and in the Jungner nickel-cadmium batteries used as button cells for calculators [47]. Here, prepared nickel oxide is pressed into a holding plate of perforated nickel. Such prepared plates of nickel(lli) oxide have been proposed as reagent for the oxidation, in alkaline solution, of secondary alcohols to ketones and primary alcohols to carboxylic acids [48]. Used plates can be regenerated by anodic oxidation. 

Benzisoxazole-3-carboxylic acid, 6-nitro-, reaction with methanolic hypochlorite, 59, 273... 

Eleven years later, a German patent described the preparation of ethyl l-azabicyclo[3.1.0]hexane-5-carboxylate (6) by the reaction of ethyl piperidine-3-carboxylate (5) with ferr-butyl hypochlorite, followed by treatment with base. 

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. 

Primary alcohol groups can also be mildly and selectively oxidized to carboxyl groups by reaction with 2,2,6,6-tetramethyl-l-piperidine oxoanunonium ion (TEMPO) in the presence of hypochlorite and bromide [129,130]. The specificity for the oxidation of primary alcohols in the presence of secondary alcohols in carbohydrates occurs because of the bulky nature of the TEMPO reagent, similar to the specificity obtained with the bulky trityl chloride. The mechanism for the oxidation of primary alcohols with TEMPO is given in reaction 4.140. 

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