Mucic acid, C6H10O8 or HOOC-(CHOH)4-COOH (galactaric acid or meso-galactaric acid) is an aldaric acid obtained by nitric acid oxidation of galactose or galactose-containing compounds such as lactose, dulcite, quercite, and most varieties of gum.[1]
Mucic acid forms a crystalline powder, which melts at 210–230 °C.[2] It is insoluble in alcohol, and nearly insoluble in cold water.[1] Due to the symmetry in the molecule, it is optically inactive even though it has chiral carbon atoms (i.e., it is a meso compound).
When heated with pyridine to 140 °C, it is converted into allomucic acid.[1] [3] When digested with fuming hydrochloric acid for some time it is converted into αα′ furfural dicarboxylic acid while on heating with barium sulfide it is transformed into α-thiophene carboxylic acid.[1] The ammonium salt yields on dry distillation carbon dioxide, ammonia, pyrrol and other substances.[1] The acid when fused with caustic alkalis yields oxalic acid.[1]
With potassium bisulfate mucic acid forms 3-hydroxy-2-pyrone by dehydration and decarboxylation.
Mucic acid can be used to replace tartaric acid in self-raising flour or fizzies.
It has been used as a precursor of adipic acid in the way to nylon by a rhenium-catalyzed deoxydehydration reaction.[4]
It has been used as a precursor of Taxol in Nicolaou Taxol total synthesis (1994).