Oxidation of Osones

The 2-keto acids such as 2-keto-D-galactonic acid (XXIV) can be derived from the corresponding osone (XXIII) by oxidation with bromine Oxidation of L-gulosone by the same method has provided 2-keto-L-gulonic acid. The success of this oxidation depends to a large extent upon the purity of the osone subjected to oxidation and this, as previously stated, is controlled by the purity of the osazone. 

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The keto aldonic acids of the hexose series are of the 2- and 5-keto types. The 2-keto acids have been called osonic acids because of their preparation by the oxidation of osones. The 5-keto acids have been termed keturonic... 

Oxidation. Acetaldehyde is readily oxidised with oxygen or air to acetic acid, acetic anhydride, and peracetic acid (see Acetic acid and derivatives). The principal product depends on the reaction conditions. Acetic acid [64-19-7] may be produced commercially by the Hquid-phase oxidation of acetaldehyde at 65°C using cobalt or manganese acetate dissolved in acetic acid as a catalyst (34). Liquid-phase oxidation in the presence of mixed acetates of copper and cobalt yields acetic anhydride [108-24-7] (35). Peroxyacetic acid or a perester is beheved to be the precursor in both syntheses. There are two commercial processes for the production of peracetic acid [79-21 -0]. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or osone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde (36). Peracetic acid can also be formed directiy by Hquid-phase oxidation at 5—50°C with a cobalt salt catalyst (37) (see Peroxides and peroxy compounds). Nitric acid oxidation of acetaldehyde yields glyoxal [107-22-2] (38,39). Oxidations of /)-xylene to terephthaHc acid [100-21-0] and of ethanol to acetic acid are activated by acetaldehyde (40,41). 

Yields of osones obtained by the oxidation of sugars by Fenton s reagent are low, and the osones are invariably contaminated both with starting material and with the products of further oxidation in consequence, the method has had only limited application.44... 

Evans, Nicoll, Strause and Waring46 oxidized D-glucose and D-fructose in aqueous solution with excess cupric acetate at 50° for the purpose of ascertaining whether the general principles underlying the mechanism of carbohydrate oxidation in alkaline solutions are sufficient to explain the course of such oxidations in acid solutions. D-Glucosone was claimed to be one of the first products of oxidation the osone was not isolated, and,... 

They showed that osone formation is accompanied by the production of formic acid, thought to arise from the oxidation of hydroxymethylene formed by rupture of IV. 

Weidenhagen48 further investigated this reaction he found that osone formation could become the main reaction if ethanol or methanol was used as a solvent, the cupric acetate was not in excess, and the reaction time was limited. Oxidation of D-glucose or D-fructose was reported to give a 40% yield of D-glucosone.14-46... 

The oxidation of D-glucose with potassium persulfate occurs very slowly at room temperature the optimum temperature is 40°, but the yield of osone is very small.38... 

In the preparation of D-glucosone by the direct oxidation of D-glucose, D-fructose, or D-mannose by such reagents as that of Fenton,37 cupric acetate,16- 46- 46 selenious acid,16-61 etc., the degree of oxidation must be carefully controlled if the osone, which is the first product, is to be the main product of the reaction. The nature and mechanism of formation of the products of further oxidation of D-glucosone are discussed on p. 68. 

Lewis201 postulated maltosone as the first product in the oxidation of maltose by Fehling solution, but no osone was detected when maltose was treated with Fenton s reagent.23 Oxidation of maltosone with bromine water gave 2-oxo-maltobionic acid, isolated as its brucine salt.191... 

These compounds are formally derived from aldoses by oxidation of a secondary hydroxyl group to a ketone group. The well-known aldos-2-uloses (usually termed simply aldosuloses or osones in former usage) have long been known in the form of their bis(hydrazone) derivatives, the osazones. Deoxyaldosuloses have been implicated as intermediates in a variety of degradation reactions. Aldos-3-, -4-, and -5-uloses have been prepared, principally as intermediates for synthesis. 

Stacey and Turton61 tried to produce the osone hydrate directly by oxidation of 2,3,4,6-tetra-0-acetyl-(2-hydroxy-D-glucal) with an ethereal solution of perbenzoic acid. A discrepancy exists in the constants reported for the specimens of 2,3,4,6-tetra-O-acetyl-D-glucosone hydrate prepared... 

In the recent, especially the patent, literature, a number of experiments are described on the direct oxidation of L-sorbose to 2-/cefo-L-gulonic acid, with chlorates,110 nitrous111 and nitric112 acids and by catalytic oxidation with platinum catalyst.113 Cupric acetate114 in methanol oxidizes L-sorbose to the osone, from which L-ascorbic acid is easily prepared. 

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