I'm having trouble determining if sugars are D/L in their chair forms. My textbook has generously provided this image of D-Glucose. enter image description here

So I know that from the fischer, when I put everything into a chair view, the things on the left point up, and the things on the right point down.

However, what about the bottom $\ce{CH2OH}$ group. Which way does it point, and does it determine D/L in a ring? I'm imagining "rotating" all the groups 1 position over clockwise (does it matter if its clockwise/counterclockwise? How do you know which way to spin it?) such that the hydroxyl is now where the $\ce{CH2OH}$ was, H is on the right and $\ce{CH2OH}$ is on the left.

Does that sound right? I can vaguely remember this from high school, but it's become very clouded.


1 Answer 1


D-glucose stays D-glucose regardless of whether it is in chair (hemiacetal) form, open chain form, or any other minor form. These different forms (if you could isolate them) would likely have different specific rotation values (interaction with plane polarized light). There are two chair forms-one with an axial OH and the other equatorial (probably favored)--but both are forms of D-glucose.


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