Linear forms and C1 chair forms of 8 possible D-aldohexoses. Naturally occurring glucose, mannose and galactose are shown in bold face. In each linear form, OH group(s) epimeric relative to glucose are shown with solid box(es). In each chair form, axial OH-group(s) are shown in red for emphasis, and hydrogen atom(s) which cause thermodynamically unfavored 1, 3-diaxial interactions are shown in bold bars (H is not shown). It is obvious that the numbers of such interactions are minimal for glucose (0), mannose (1) and galactose (1). For simplicity, all of the pyranose structures are drawn as C1 conformers of b-anomers.