Ruff oxidative degradation

G. Hourdin, The catalysis of the Ruff oxidative degradation of aldonic acids by titanium-containing zeolites, Catal. Lett., 69 (2000) 241-244. 

AN ORIGINAL BEHAVIOUR OF COPPER(II)-EXCHANGED Y FAUJASITE IN THE RUFF OXIDATIVE DEGRADATION OF CALCIUM GLUCONATE... 

Starting from a salt of an aldonic acid, the Ruff oxidative degradation reaction1 leads to an aldose with loss of one carbon atom. Known since 1898, the original process used aqueous hydrogen peroxide as oxidant, in the presence of catalytic amounts of ferric salts. 

Copper(II)-exchanged Y Faujasite in the Ruff Oxidative Degradation of Calcium Gluconate... 

Titanium-containing zeolites, such as Ti-BEA, Ti-FAU, and TS-1 have been tested as catalysts for the Ruff oxidative degradation of calcium D-gluconate 72 to D-arabinose 55 using diluted hydrogen peroxide as the oxidant. Only large-pore zeolites Ti-BEA and Ti-FAU were found to be active. It was shown, in particular, that a very rapid leaching of titanium occurred and that the titanium species present in the solution were responsible for the catalytic activity observed [67,68]. 

RUFF - FENTON Degradation Oxidative degradation of aldoses via a-hydroxy acids to lower chain aldoses. 

Ruff-Fenton degradation. Shortening of the carbon chain of sugars by the oxidation of aldonic acids (as calcium salts) with hydrogen peroxide and ferric salts. 

Robinson Annulation Robinson-Schopf Reaction Rosenmund Reduction Rosenmund-von Braun Synthesis Rothemund Reaction Rubottom Oxidation Ruff-Fenton Degradation Rupe Rearrangement Ruzicka Large Ring Synthesis Sabatier-Senderens Reduction Sachs (see Ehrlich-Sachs Reaction)... 

Problem 22.20 Two Ruff degradations of an aldohexose give an aldotetrose that is oxidized by HNO, to /n o-tartaric acid. What can be the family configuration of the aldohexose ... 

Problem 22.28 An aldohexose (I) is oxidized by HNO, to a me o-aldaric acid (II). Ruff degradation of (I) yields (III), which is oxidized to an optically active dicarboxylic acid (IV). Ruff degradation of (III) yields (V), which is oxidized to l-( + )-tartaric acid (VI). Represent compounds (I) through (VI). M... 

Problem 22.60 Which D-pentose is oxidized to an optically inactive dibasic acid and undergoes a Ruff degradation to a tetrose whose glycaric acid is meso-tartaric acid ... 

Two useful preparations of lower sugars by degradation of aldonic acids are discussed in the following Chapter. These are the traditional oxidation of salts of aldonic acids with hydrogen peroxide in the presence of ferric acetate (Ruff degradation) and the related oxidation of aldonic acids by hypochlorite, which was developed by Whistler and Schweiger.79... 

Ferric ion catalyzes the formation of the hydroperoxyl radical, according to Eq. (35) such a radical appears to constitute the oxidant in the Ruff method of degrading aldonic acids to the next lower aldoses. A number of examples of the use of this reagent in the laboratory are given in a review article by Moody.108 The hydroperoxyl radical, which is not so effective an oxidant as the hydroxyl radical, does not attack aliphatic alcohols accordingly, a substantial yield (about 50%) of the aldose is obtained from the higher aldonic acid. In the presence of an excess of hydrogen peroxide, however, the accumulation of ferrous ions in solution catalyzes the production of hydroxyl radicals and lowers the yield of aldose [see Eq. (36)]. 

For another reaction, i.e. Ruff s carbohydrate degradation [46], the origin of the true oxidant is also unclear. The reaction between a-oxyacids and H202 in the presence of trivalent ferric salts is presented by the following overall reaction ... 

Ruff degradation followed by HNO3 oxidation gives an optically inactive aldaric acid. 

Two Ruff degradations followed by HNO3 oxidation give meso-tartaric acid. 

Copper(II)-exchanged faujasite was tested in the Ruff degradation of calcium gluconate and compared, under the same reaction conditions, with homogeneous catalysis by copper(II) sulphate. The amount of copper was the same in both cases and the reactions were stopped when hydrogen peroxide was totally consumed. D-arabinose and D-erythrose were the main products, glyceraldehyde was formed in small amount 2% yield). Blank experiment was carried out with the starting Na-faujasite, for the same reaction time as the one required for the oxidation in presence of copper zeolite. 

The aldonic acids of the pentose series were prepared similarly. L-Arabonic acid was isolated by Kiliani as the calcium salt, and Ruff prepared calcium n-arabonate. In the latter case almost quantitative yields were reported. n-Lyxonic acid was isolated as the basic lead salt and converted to the crystalline lactone by Wohl and List. n-Ribose was oxidized to the crystalline cadmium n-ribonate by Levene and Jacobs the yield was less than 50%. The well-known boat-shaped crystals of the double salt of cadmium n-xylonate-cadmium bromide were prepared by the oxidation of n-xylose with an excess of bromine by Ruff, followed by a subsequent treatment with cadmium carbonate. Ruff also prepared L-erythronic acid, isolating it as the brucine salt the starting material was a crude n-erythrose sirup prepared by degradation of calcium L-arabonate. 

The well-known Ruff degradation of aldonic acids to aldoses with one less carbon was first applied with bromine as the oxidant. Calcium D-gluconate was treated with an excess of bromine at 20° for ten hours the acidity of the solution was kept low with lead carbonate. The filtrate was processed and D-arabinose was obtained in small yield as the oxime. However, Ruff found that the effect of hydrogen peroxide was much better and abandoned the use of bromine. Fenton noted the same effect in the oxidation of tartaric acid to dihydroxymaleic acid the action of oxygen was more effective than that of the halogens. It was assumed that a keto aldonic acid was the intermediate in the degradation of the aldonic acid to the new aldose, and the apparent stability of the keto acids to further oxidation by bromine may be the reason for the low yields with this oxidant. 

Ruff noticed in the mother liquors of an erythrose preparation obtained by degradation of L-arabonic acid, a small amount of another sugar, apparently a keto tetrose, which was not oxidized by bromine. The ketose gave the same phenylosazone as that obtained from L-ery-throse, but was not isolated otherwise. Neuberg oxidized erythritol to form an optically inactive tetrose solution and claimed that color reactions showed the presence of a keto tetrose. 

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