From straight chain to chair structure?

[theyellowking]

This is not asking of how to convert a chain to a Haworth projection (Right down, left up), but how you would know which groups on a sugar from a chain form are either equatorial or axial when drawing the chair form of the sugar's ring structure.

For example, how would you know looking from glucose in its chain form that all of its substituents have equatorial orientation in B-D-glucopyranose form, or that B-D-mannopyranose has substituents that are equatorial except C-2? Although I understand that memorizing that B-D-glucopyranose's substituents are all equatorial leads you to the other chair structures of manno and galacto, how did you get the chair structure of glucopyranose in the first place? I know memorizing it will solve the problem, but I'm interested if there's a method of approach.

Tl;DR Do you simply have to memorize that B-D-glucopyranose's substituents are all equatorial, or is there a method of converting from the chain form?

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[ayocaptain628]

This is not asking of how to convert a chain to a Haworth projection (Right down, left up), but how you would know which groups on a sugar from a chain form are either equatorial or axial when drawing the chair form of the sugar's ring structure.

For example, how would you know looking from glucose in its chain form that all of its substituents have equatorial orientation in B-D-glucopyranose form, or that B-D-mannopyranose has substituents that are equatorial except C-2? Although I understand that memorizing that B-D-glucopyranose's substituents are all equatorial leads you to the other chair structures of manno and galacto, how did you get the chair structure of glucopyranose in the first place? I know memorizing it will solve the problem, but I'm interested if there's a method of approach.

Tl;DR Do you simply have to memorize that B-D-glucopyranose's substituents are all equatorial, or is there a method of converting from the chain form?

what do you mean by chain form, what does that look like?

 

[theyellowking]

Sorry, I should have clarified. I meant a Fischer projection

 

[Czarcasm]

Sorry, I should have clarified. I meant a Fischer projection

In fischer, horizontal lines are wedges, vertical lines are dashes. For glucose, it's probably best to use your right hand and stick out your middle finger. Your pointer finger, ring finger, and index finger (all point left) indicate -OH's pointing left. Your middle finger indicates the -OH pointing right. I've taken this mneumonic from TBR. They have a few others, but this is the only one worth knowing imo.

As far as converting fischer to haworth, I use the saying: "Down Right, Up-Lefting" - so anything on the right side points down, anything on the left side points up. These two tid bits of info have really helped.

 

[ayocaptain628]

Sorry, I should have clarified. I meant a Fischer projection

providing images would be helpful

 

[BerkReviewTeach]

This is not asking of how to convert a chain to a Haworth projection (Right down, left up), but how you would know which groups on a sugar from a chain form are either equatorial or axial when drawing the chair form of the sugar's ring structure.

For example, how would you know looking from glucose in its chain form that all of its substituents have equatorial orientation in B-D-glucopyranose form, or that B-D-mannopyranose has substituents that are equatorial except C-2? Although I understand that memorizing that B-D-glucopyranose's substituents are all equatorial leads you to the other chair structures of manno and galacto, how did you get the chair structure of glucopyranose in the first place? I know memorizing it will solve the problem, but I'm interested if there's a method of approach.

Tl;DR Do you simply have to memorize that B-D-glucopyranose's substituents are all equatorial, or is there a method of converting from the chain form?

The BR method you are describing for chair confirmations (where ß-D-Glucopyranose has everything in equatorial and from there you simply put any epimeric hydroxyl groups axial for other sugars) works really well. You should use that method. But if you need to know how it was derived, it came from converting up and down hydroxyl groups in the Haworth projection into axial and equatorial groups in the chair conformation. Keep in mind that on a chair structure, up-axial alternates with up-equatorial on neighboring carbons. This is why down/up/down for the hydroxyl groups on C2, C3, and C4 of glucose are equatorial-down/equatorial-up/equatorial-down in the chair conformation. Drawing them out side by side should help.