Galactaric

Galactaric acid, also known as saccharic acid derived from galactose, is an aldaric acid produced by the oxidative cleavage of the terminal carbon atoms of galactose. In its open-chain form, the molecule is a hexaric acid with carboxyl groups at both ends and four hydroxyl-bearing carbons in between, commonly described as HOOC-(CHOH)4-COOH. Because it is derived from galactose, galactaric acid is considered a hexaric, or aldaric, acid.

Preparation and properties

Galactaric acid is formed by strong oxidation of galactose, using reagents such as nitric acid or other potent oxidants. The process converts both the aldehyde group at C1 and the primary alcohol at C6 of galactose into carboxyl groups, yielding the dicarboxylic acid. The compound readily forms water-soluble salts with alkali and alkaline earth metals. It is usually isolated as its neutral acid or as various salts, such as sodium galactarate.

Relationship to other aldaric acids

Galactaric acid is part of a family of aldaric acids that also includes glucaric acid (from glucose) and related species derived from other aldoses. These acids are frequently discussed in carbohydrate chemistry as products of oxidative cleavage and as historical reagents for studying sugar structures and reactivity.

Uses and context

Historically, aldaric acids like galactaric acid have served as references and intermediates in carbohydrate chemistry and analytical methods. Today, they are mainly of academic interest or used in niche chemical syntheses rather than as bulk industrial feedstocks.