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Topic: Glucose Mutarotation  (Read 1408 times)

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Offline Aurt

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Glucose Mutarotation
« on: May 24, 2024, 03:47:47 AM »
Hello. I have been having issues regarding mutarotation of glucose. I've looked up several sources on the internet regarding the interconversion of α-glucose to β-glucose and vice versa (even tried chatgpt), but the most i come up with is "yes it happens". So now I am kind of stuck at one point going round and round about it.
So without further delay... My question is basically regarding the fundamental chemistry of glucose in terms of opening and closing the glucose structure on addition of it to water. The web states that mutarotation takes place in order to maintain equilibrium...but it fails to pinpoint exactly why both forms of glucose are even required (especially when β form is more stable).
I have discerned that this whole phenomenon primarily has to do with the linkage between the anomeric carbon and the 5th carbon in the molecule, namely the hemiacetal bond or glycosidic bond forming the cyclic structure.
I am interested in detailed chemistry behind that particular bond itself, and as to how water is factor in breaking and joining the cyclic structure. Does it also have to do with the aldehyde group in the linear structure that forms the hemiacetal in glucopyranose?
Also protonation and deprotonation of the solution results in increasing rate of mutarotation as well. But in case of extremely alkaline conditions they structure also breaks down or changes to other molecules like galactose or fructose. So is there a certain threshold in alkalinity where glucose can be stored without changing the rate of mutarotation or possibly degrading/deforming the structure?
With all due respect I am not exactly looking for a bookish answer. I am exclusively looking to increase my own knowledge regarding this, so anyone kind of to reply please feel free to use your own words however convenient.
Thanks a lot!

Offline Babcock_Hall

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Re: Glucose Mutarotation
« Reply #1 on: May 24, 2024, 09:55:26 AM »

You have asked more questions than I can answer.  The beta-anomer is only slightly more stable than the alpha-anomer; therefore, the equilibrium between them is only about 64:36.  Regarding rates of reaction in water, specific acid catalysis is the speeding up of a reaction due to protons.  The definition of specific base catalysis is analogous.  General acid catalysis is the speeding up of a reaction in the presence of a weak acid at constant pH, and the definition of general base catalysis is analogous.  The paper above may answer some of your questions.

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