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Topic: How to Convert Haworth to Chair and Vise-Versa  (Read 3960 times)

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Offline StevenUSF

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How to Convert Haworth to Chair and Vise-Versa
« on: September 11, 2014, 09:12:09 PM »
When a sugar is in a chair conformation the hydroxyl groups are all equatorial with the exception of the anomeric carbon which can switch between axial and equatorial via a ring opening tautomerization. When going from chair to Haworth how do I know whether the hydroxyl groups are up or down?

I included an attachment showing an example of two alpha anomers and two beta anomers that have the same chair conformation.

Offline Dan

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Re: How to Convert Haworth to Chair and Vise-Versa
« Reply #1 on: September 12, 2014, 12:28:30 AM »
Draw in the axial Hs in as well, it will make it much easier to see.
My research: Google Scholar and Researchgate

Offline Babcock_Hall

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Re: How to Convert Haworth to Chair and Vise-Versa
« Reply #2 on: September 12, 2014, 09:28:05 AM »
When a sugar is in a chair conformation the hydroxyl groups are all equatorial with the exception of the anomeric carbon which can switch between axial and equatorial via a ring opening tautomerization.
One problem with what you wrote is that the all-equatorial statement is only true for glucose, not galactose or mannose, for example.  A second problem is that tautomerizations are isomerizations in which only hydrogen atoms move.

Offline StevenUSF

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Re: How to Convert Haworth to Chair and Vise-Versa
« Reply #3 on: September 15, 2014, 08:16:44 AM »
I'm still confused. Here are two different sugars in haworth and their respective chair conformations. The pink -OH is up in each Haworth, but up and down in the two chair conformations. If given a chair, how do I know whether a -OH is up or down in the Haworth? Thank you for helping me :D

Draw in the axial Hs in as well, it will make it much easier to see.
How do I know if they are axial in the first place? Don't I have to go based on whether the -OH is up or down in the haworth?

Offline Dan

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Re: How to Convert Haworth to Chair and Vise-Versa
« Reply #4 on: September 15, 2014, 10:50:44 AM »
Ok, let's start with the basics: can you draw tetrahydropyran in chair conformation showing all the H atoms?

Note that your Haworth-chair conversion for L-glucose is incorrect, but don't worry about that yet, start with tetrahydropyran.
My research: Google Scholar and Researchgate

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