Final answer:
Galactose can exist in two main tautomeric cyclic forms, alpha (α) and beta (β), distinguished by the orientation of the hydroxyl group at the anomeric carbon; this continuous interconversion is called mutarotation.
Step-by-step explanation:
The number of tautomeric forms in galactose relates to its ability to exist in different isomeric configurations due to the interchange of atoms within its molecule. In the case of galactose, this mainly pertains to the different cyclic hemiacetal forms it can adopt through the mutarotation process. Specifically, galactose, being an aldohexose like glucose, can exist in two main cyclic forms, designated as alpha (α) and beta (β), which differ in the spatial arrangement of the hydroxyl group (OH) at the anomeric carbon (carbon 1). Similar to glucose, when dissolved in water, galactose achieves a dynamic equilibrium between its α and β forms, as well as a minute amount of the straight-chain form.
Considering the stereochemistry at the anomeric carbon, the cyclic forms of galactose are known as α-D-galactopyranose and β-D-galactopyranose, reflecting the axial or equatorial orientation of the hydroxyl group at that specific carbon. The interconversion between these tautomeric forms occurs continuously in aqueous solution and is a manifestation of mutarotation. Hence, galactose has two main tautomeric forms.