Galactaric acid

Oxidation of tiie caibon atoms at both ends of the carbon chain produces an aldaric acid. That made from D-galactose is galactaric acid [526-99-8] a... 

Mucic Acid (Galactaric acid, Galactosaccharic acid, Tetrahydroxyadipic acid, Saccharolactic acid.Schleimsaure (Ger). 

To the names of aldaric acids that are symmetrical, which therefore have no D- or L- prefix, the prefix meso- may be added for the sake of clarity. Examples mero-erythraric acid, meso-ribaric acid, meso-xylaric acid, meso-allaric acid, meso-galactaric acid. 

When an oxidizing agent, e.g. nitric acid, is used, a sugar is oxidized at both ends of the chain to the dicarboxylic acid, called aldaric acid. For example, galactose is oxidized to galactaric acid by nitric acid. 

Galactaric Acid (mucic acid) [526-99-6] M 210.1, m 212-213°(dec). Dissolved in the minimum volume of dil aq NaOH, and ppted by adding dil HCI. The temperature should be kept below 25°. 

Arabinose—as could be shown by chain extension and degrading of glucose and mannose—forms a portion of both of these hexoses its configuration can be neither that of ribose, nor that of xylose, because, in contrast to arabinose, these pentoses form inactive dicarboxylic acids. The formula (7) (lyxose) is ruled out for arabinose, since a one-carbon addition to it leads to an inactive (galactaric) acid and an active (talaric) acid. Consequently, D-arabinose must have formula (5) and with that conclusion, (10) had been derived for D-(+)-glucose—but with one restriction. Fischer had to choose between (10) and its enantiomorph he chose (10), and wqs aware of the arbitrary nature of this decision. The same decision fixed the form of all the other series-related sugars represented in Fig. 1. That Fischer had accidentally chosen the correct absolute configuration was not realized until after his death. 

It now became clear that the (-H-tartaric acid produced by oxidation of n-saccharic (n-glucaric) acid is formed from its first four carbon atoms, and that racemic tartaric acid (31 + 32) is produced in the same manner, from mucic (galactaric) acid (19). The choice of formula (31) for (+)-... 

D-galactaric acid, 213 Penta-acetate, a- 74, / - 115 Penta-acetate, a- 59, / - 126 Penta-acetate, a- 94, /J- 86... 

Escherichia coli metabolizes D-glucaric acid and galactaric acid to give respectively 3-deoxy-D-eryt/zro-2-hexulosaric and 3-deoxy-h-threo-2-hexulosaric acids.268... 

The reaction probably proceeds via the cyclic forms of the sugars and lactones, as equilibria between the various cyclic forms and the acyclic form are presumably established rapidly under the strongly acidic conditions of these oxidations. Thus, D-galactose undergoes oxidation to (acyclic) galactaric acid, whereas similar reaction of D-mannose affords a dilactone (see preceding Chapter). 

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