Sugar acids mucic acid

Pyrrole and the simple alkyl-pyrroles are colourless liquids, with relatively weak odours rather like that of aniline, which, also like the anilines, darken by autoxidation. Pyrrole itself is readily available commercially, and is manufactured by alumina-catalysed gas-phase interaction of furan and ammonia. Pyrrole was first isolated from coal tar in 1834 and then in 1857 from the pyrolysate of bone, the chemistry of which is similar to an early laboratory method for the preparation of pyrrole - the pyrolysis of the ammonium salt of the sugar acid, mucic acid. The word pyrrole is derived from the Greek for red, which refers to the bright red colour which pyrrole imparts to a pinewood shaving moistened with concentrated hydrochloric acid. 

Pyrrole was first isolated in 1857 from the pyrolysate of bone the process by which it arises is similar to an early laboratory method for the preparation of pyrrole - the pyrolysis of the ammonium salt of the sugar acid, mucic acid. 

Oxidation of galactose (or a galactose-containing sugar) to mucic acid. Dissolve 1 g. of galactose or lactose in a mixture of 10 ml. of water and 5 ml. of concentrated nitric acid contained in a small evaporating dish, and evaporate the solution to dryness on a water bath. Stir the cold residue with 10 ml. of cold water, filter off the mucic acid, wash it with cold water, dry and determine the m.p. (212-213° with decomposition). 

MUchzucker, m. milk sugar, lactose, -agar, m. lactose agar, -saure, /. saccholactic acid (mucic acid). 

The mucic acid test is now only of historical interest. It depends on the oxidation of galactose or saccharides containing a galactose residue, such as lactose, with nitric acid to yield mucic acid. Mucic acid is highly insoluble in water, while the isomeric dicarboxylic acids yielded by other sugars are soluble. Mucic acid may be identified by its characteristic thallium salt. 

In a similar fashion it should be a relatively simple task to relate the well-known D-gala-L-manno-heptose (XX) to a-rhamnohexose (XXII)81 through the known 1-desoxy-D-gala-L-mcmno-heptitol (syn., 7-desoxy-L-manno-L- aZa-heptitol) (XXI).81 In. this particular case, however, there is already ample proof of the configuration of the latter sugar (XXII) because nitric acid has been found to oxidize the corresponding aldonic acid to mucic acid.82... 

The conversion of the synthetic 4-(/3-D-galactopyranosyl)-D-mannose (epilactose) through the hexaacetyllactal to lactose forms the keystone in the total synthesis of this sugar.61-62 Proof of the structure of 4-(/3-D-gal-actopyranosyl)-D-mannose was accomplished by hydrolyzing it with hydrochloric acid, and also with emulsin, to D-galactose (identified by oxidation to mucic acid) and D-mannose (identified as its phenylhydrazone).18... 

Crystallization sugars may easily crystallize. The crystals are usually stable at room temperature, although in general are hygroscopic and they have to be held in a closed vessel. Sugars are present in wines at very low concentration thus they remain soluble. Nevertheless some problems can arise when some insoluble crystals appear, such as mucic acid (galactaric). 

Pyrrole and N-substituted pyrroles are formed by a reaction analogous to the conversion of sugars to furan aldehydes. Ammonium and substituted ammonium salts of mucic acid, H02C(CH0H)4C0jH, are cyclized and de-carboxylated by pyrolysis. The yields of pyrrole and its N-phenyl and N-methyl derivatives are about 40%. Tetrahydropyrroles (pyrrolidines) are formed from various 4-substituted amines by elimination of water, ammonia, or hydrogen halide. ... 

Panzer obtained a gel-like carbohydrate substance from defatted bacilli (human strain) by successive extraction with water, hydrochloric acid, sodium carbonate, sodium nitrate, hot water and potassium hydroxide. The resulting liquors each yielded a gum-like substance which was sulfur-, nitrogen- and phosphorus-free. Oxidation of this derivative with nitric acid gave oxalic acid but no mucic acid. Panzer concluded that the substance was probably a pectin but not a galactan. It is now known that drastic oxidation of this nature would give oxalic acid from any sugar derivative. It is possible that by using controlled oxidation, mucic acid could be obtained from this carbohydrate. 

The tank cell has found an interesting and elegant application in the sugar industry [44]. A modified Grignard reactor is used for the scale-up of the indirect oxidation of galacturonic acid [45] (Scheme 1). A vessel equipped with a mechanical stirrer and cylin-drically shaped electrodes is used to produce mucic acid. The reaction conditions are given in detail in Ref. 46. 

Examination of the active hydrocolloid followed the usual systematic pattern. Proximate analyses were first noted, and then the carbohydrate nature of the components was determined. Galactose was identified as the major product of hydrolysis by oxidation to mucic acid (5, -4, 12, 17) and by optical rotation (17). Glucose (16, 28), fructose (17) or keto sugars (28, UO), pentoses (28, 35), and nonreducing sugars (9) were also found. However, the presence of glucose is attributed by... 

Oxalic acid, separated from sorrel through the lead salt, was shown (1784-1785) to exist in rhubarb and other vegetables as the calcium salt ( earth of rhubarb ), and was proved to be the same as the acid formed by the action of nitric acid on malic acid or cane sugar. By oxidising milk sugar with nitric acid Scheele in 1780 obtained both oxalic acid and a new insoluble acid (acidum sacchari lactis acidum galacto-saccharinum), viz. mucic acid, and by heating mucic acid, a sublimate of pyromucic acid. ... 

Oxidations with nitric acid under the best conditions convert primary alcoholic and aldehydic groups to carboxylic groups. Frequently, however, cleavage of carbon-carbon bonds occurs. For galactose the conversion to insoluble mucic acid, COOH—(CHOH)4—COOH, takes place to an extent greater than 70 %, and the reaction is used for the quantitative determination of this sugar (229, 230). This oxidation has been halted before completion and a 10% yield of the L-galacturonic acid obtained (231). Smaller... 

Alternatively, the reaction may proceed via the ring forms of the sugars and the lactones, but this refinement of the mechanism has not been clarified. Under the strongly acidic conditions of these oxidations, equilibria between the various ring and open-chain forms should be established quickly. In this connection, it should be noted that whereas galactose gives mucic acid (the open-chain form), mannonic acid gives a dilactone. 

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