Sodium hypochlorite, alcohol oxidation with

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also long been used in the manufacture of the positive pole in the Edison nickel-iron rechargeable battery, now largely superseded by die lead-acid accumulator, and in the Jungner nickel-cadmium batteries used as button cells for calculators [47].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. 

Oxidation of CHOH (7, 337). Sodium hypochlorite solutions1 oxidize secondary alcohols dissolved in acetic acid to ketones in yields of 90-95%. Selective oxidation in the presence of a primary alcohol group is possible. The oxidation has been conducted, with suitable precautions, on a large scale.2... 

The stable, commercially available nitroxyl radical 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) 51 is an excellent catalyst, in conjunction with a co-oxidant, for the oxidation of alcohols. The most popular co-oxidant is buffered sodium hypochlorite (NaOCl). Oxidation of the nitroxyl radical gives the oxoammonium ion 52, which acts as the oxidant for the alcohol to form the carbonyl product. Primary alcohols are oxidized faster than secondary and it is often possible to obtain high chemoselectivity for the former. For example, oxidation of the triol 53 gave the aldehyde 54, with no oxidation of the secondary alcohols (6.44). The use of TEMPO is particularly convenient for the oxidation of primary alcohols in carbohydrates, avoiding the need for protection of the secondary alcohols. 

Oxidative Methods.—A convenient and inexpensive procedure for the oxidation of secondary alcohols to ketones, applicable to multi-mole preparations, uses aqueous sodium hypochlorite in acetic acid/ Selective oxidation of secondary alcohols is possible as primary alcohols are oxidized much more slowly. Alcohol oxidations with molecular bromine in combination with nickel(ll) benzoate in acetonitrile are remarkably free from competing reactions. However, 1,4-diols yield butyrolactones. ... 

Oxidation of —CHtOH — —CHO (cf., 12,479-480). This oxidation can be effected in high yield with sodium hypochlorite (slight excess) in buffered H20/ CH2C12 with this nitroxyl radical and KBr as the catalysts.1 The oxidation is exothermic, and the temperature should be maintained at 0-15° with a salt-ice bath. Saturated primary alcohols are converted to aldehydes in 88-93% yield yields are lower in the case of unsaturated substrates. Addition of quaternary onium salts permits further oxidation to carboxylic acids. 

L. Gosalvi, 1. W. C. E. Arends, P. Moilanen, R. A. Sheldon, The Effect of pH Control on the Selective Ruthenium-Catalyzed Oxidation of Ethers and Alcohols with Sodium Hypochlorite, Synth Catal. 345 (2003) 1321—1328. 

In another procedure, oxidation is carried out in the presence of chloride ions and ruthenium dioxide [31]. Chlorine is generated at the anode and this oxidises ruthenium to the tetroxide level. The reaction medium is aqueous sodium chloride with an inert solvent for the alkanol. Ruthenium tetroxide dissolves in the organic layer and effects oxidation of the alkanol. An undivided cell is used so that the chlorine generated at the anode reacts with hydroxide generated at the cathode to form hypochlorite. Thus this electrochemical process is equivalent to the oxidation of alkanols by ruthenium dioxide and a stoichiometric amount of sodium hypochlorite. Secondary alcohols are oxidised to ketones in excellent yields. 1,4- and 1,5-Diols with at least one primary alcohol function, are oxidised to lactones while... 

A convenient procedure for the oxidation of primary and secondary alcohols was reported by Anelli and co-workers (8,9). The oxidation was carried out in CH2CI2 with an aqueous buffer at pH 8.5-9.5 utilizing 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO, 1) as the catalyst and KBr as a co-catalyst. The terminal oxidant in this system was NaOCl. The major disadvantage of using sodium hypochlorite or any other hypohalite as a stoichiometric oxidant is that for each mole of alcohol oxidized during the reaction one mole of halogenated salt is formed. Furthermore,... 

The traditional method of oxidizing hydrazine derivatives makes use of halogens or hypohalites as oxidizing agents. The techniques range from the preparation of l,l -azobis(l-cyclohexanenitrile) by the addition of bromine to an alcoholic hydrochloric acid solution of the corresponding hydrazine [89], through the use of bromine water [90, 91] to oxidations with sodium hypo-bromite [64] or sodium hypochlorite [92]. 

Apart from the activation of the anode no reagent has to be produced. Nickel peroxide, however, has to be prepared by oxidation of nickel(II)sulfate with sodium hypochlorite. Subsequently the reagent has to be carefully dried and the amount of active oxygen determined by iodometric titration. This must be kept in mind, because small amounts of alcohol need already a relative large amount of nickel peroxide, e.g. 100 mmol alcohol more than 75 g nickel peroxide. For that reason the use of the relative expensive, commercial nickel peroxide is restricted. 

Although NaI04 or KI04 are the secondary oxidants used in the vast majority of cases in which alcohols are oxidized with catalytic Ru04, the employment of sodium hypochlorite (NaOCl),31 sodium bromate (NaBrOj )32 or Cl+, electrolytic-ally generated by oxidation of chloride ion,33 have also been reported. 

Immobilized TEMPO has been used for the one-pot oxidation of alcohols to carboxylic acids as well.26 For this purpose TEMPO resin 1 was combined with two ion-exchange resins loaded with chlorite anions and hydrogen phosphate in the presence of catalytic amounts of potassium bromide and sodium hypochlorite in solution. The reaction required work-up for the removal of salts, but tolerated several protecting schemes and afforded pure products in good to excellent yields. The reaction is initiated by catalytic TEMPO oxidation of alcohols to aldehydes driven by dissolved hypochlorite followed by oxidation to the carboxylic acids effected by chlorite. 

The oxidation of alcohols to carbonyl compounds with the stable nitroxyl radical TEMPO (86) as catalyst is a well-known preparative method [134, 135]. Hypochlorite or peracetic acid is usually used as the final oxidizing agent and ca. 1 mol% of catalyst 86 is used. In 1996 Rychnovsky et al. reported the synthesis of the chiral, binaphthyl-derived TEMPO analog 87 [136], Results obtained by use of 0.5-1 mol% of catalyst 87 [136] are listed in Table 10.12. In these oxidation reactions 0.6-0.7 equiv. sodium hypochlorite were used as the final oxidizing agent (plus... 

The 2,2,6,6-tetramethylpiperidinoxyl (TEMPO) radical was first prepared in 1960 by Lebedev and Kazarnovskii by oxidation of its piperidine precursor. TEMPO is a highly persistent radical, resistant to air and moisture, which is stabilized primarily by the steric hindrance of the NO-bond. Paramagnetic TEMPO radicals can be used as powerful spin probes for investigating the structure and dynamics of biopolymers such as proteins, DNA, and synthetic polymers by ESR spectroscopy [7]. A versatile redox chemistry has been reported for TEMPO radicals. The radical species can be transformed by two-electron reduction into the respective hydroxyl-amine or by two-electron oxidation into the oxoammonium salt [8]. One-electron oxidations involving oxoammonium salts have also been postulated [9]. The TEMPO radical is usually employed under phase-transfer conditions with, e.g., sodium hypochlorite as activating oxidant in the aqueous phase. In oxidations of primary alcohols carboxylic acids are often formed by over-oxidation, in addition to the de-... 

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