Monday, 18 January 2016

carbohydrates - Which conformer of beta D-glucose is more stable?


I drew the two chair conformers of $ \beta $-D-glucose: enter image description here


Which one is more stable?


I think it's the one with all of the OH groups in the equatorial position because of less steric hindrance, but I also know that the anomeric effect makes the axial one favored as well. So I'm unsure which is more stable.



Answer




I also know that the anomeric effect makes the axial one favored as well.




The anomeric effect does stabilize an axial group, but only at the anomeric position. Other axial groups are not similarly stabilized. Thus $\alpha$-D-glucose is more stable than you think it should be based on steric considerations alone.


Knowing this, which is the more stable?


PS - very pretty chairs.


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