I want to study several carbohydrates that includes but not limited to the following molecules:

  1. Glucose
  2. Galactose
  3. Mannose
  4. Fructose
  5. Tagatose
  6. Sorbose

I know that for any carbohydrate, possible list of carbohydrates isomers are

  1. single chain (L and D isomer)
  2. $\alpha$ and $\beta$ pyranose or six member ring structures
  3. $\alpha$ and $\beta$ furanose or five member ring structures.

Now, for ring structures there are several rotamers, mainly gg, gt and tg (g=gauche, t=trans) and also there are several anomers but I am not sure about them. Is there anything I'm missing?

For accurate thorough computational study, I need to identify all the isomers. Is there any single book or document that can guide me to screen the full potential energy surface?

Thanks for your kind help.


1 Answer 1


There are 32 isomers of C6H12O6, of which you have named 6. The most common one is D-glucose (dextrose). I don't think all of the 16 L-saccharides are found in nature.

α and β refer to the connection between rings, whether the ketal (or aldehyde) oxygen is axial or equatorial.
α- and β- linkages D-Pyranoses Structures made with ChemDraw.

  • 1
    $\begingroup$ Worth noting that $\alpha$ and $\beta$ conformations will interconvert with each other in solution, in the case of single, unsubstituted rings (i.e. hemiacetals equilibrate, acetals do not). So $\alpha$-D-glucopyranose and $\beta$-D-glucopyranose will interconvert in solution, as will any $\alpha$ and $\beta$ pair in the awesome chart above. But e.g. cellulose is a polymer of $\beta$-D-glucopyranose monomers, and in the polymer, there is no significant interconversion to $\alpha$. $\endgroup$
    – Curt F.
    Jul 6, 2015 at 15:26
  • $\begingroup$ I'm using this two figures almost everyday and they are actually very handy to remove any confusion regarding structures. Thank you! Can you please give me something similar for open chain structures? Thanks! $\endgroup$ Aug 19, 2015 at 20:41
  • 1
    $\begingroup$ You can get ChemDraw for free and have all the structures you need available from the templates. acdlabs.com/resources/freeware $\endgroup$
    – LDC3
    Aug 20, 2015 at 1:04

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