D & L Glucose: Haworth Formula Explained

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The discussion centers on the representation of D-glucose in the Haworth formula, specifically addressing a perceived inconsistency regarding the orientation of the penultimate carbon (C5). The confusion arises from the claim that both structures represent D-glucose despite C5 having a hydrogen atom on the right side instead of a hydroxyl group, which traditionally indicates L-glucose. The explanation provided involves the concept of bond rotation around the C4-C5 axis, allowing for rapid adjustments in molecular conformation without altering stereochemistry. This flexibility is likened to a tripod, helping to visualize the molecular structure. Additionally, there is a shared sentiment regarding the complexity of the D/L nomenclature, with some expressing frustration over its retention and understanding.
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It is a rotation around the axis defined by the C4-C5 bond by 60°. Bonds are allowed to rotate, and do so very quickly without changing stereochemistry. Imagine the three substituents on C5 as the legs of a tripod, with the camera or whatnot as the rest of the molecule, and you may be able to see it better.

Refer to this link for an idea about D/L. For what it's worth, I agree with that author about the whole D/L convention. It always annoyed me and I never retained that information beyond whatever exam I needed to know it for.
 
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