Fructose - beta - sucrose

[DingDongD]

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http://wpage.unina.it/petrilli/gifs/sucrose.gif

In the picture, fructose has a beta position, even though it is "down." Why is that?

Thank you, ahead.

 

[aldol16]

Whether what is up or down? I'm assuming you mean the hydroxyl group attached to the anomeric carbon. Whether it's "up" or "down" tell you nothing about the anomeric form. What's important is the relative position (up vs. down) compared to C6.

 

[OrangeMed]

http://wpage.unina.it/petrilli/gifs/sucrose.gif

In the picture, fructose has a beta position, even though it is "down." Why is that?

Thank you, ahead.

You may find going through this website useful as it certainly helped me: http://mcat-review.org/carbohydrates.php

 

[theonlytycrane]

also for reference: http://forums.studentdoctor.net/threads/glycosidic-bond-in-sucrose-why-b-fructose.1181760/

 

[To be MD]

http://wpage.unina.it/petrilli/gifs/sucrose.gif

In the picture, fructose has a beta position, even though it is "down." Why is that?

Thank you, ahead.

When you're checking for alpha/beta positition, you're looking at (1) the anomeric carbon's -OH group and then (2) the posistion of -CH2OH on the other side of the - O - of the anomeric carbon. If both of these group are on the same side, it's Beta. If they're on opposite sides, it's Alpha.

If you look at fructose side of the ring, you see the -OH group that on the anomeric carbon (the one involved in the bond that has lost its H) is DOWN (1).... now you look at the CH2OH on the other side of the O... (2) it's also pointed DOWN.

So, Beta.

 

[Astra]

When you're checking for alpha/beta positition, you're looking at (1) the anomeric carbon's -OH group and then (2) the posistion of -CH2OH on the other side of the - O - of the anomeric carbon. If both of these group are on the same side, it's Beta. If they're on opposite sides, it's Alpha.

If you look at fructose side of the ring, you see the -OH group that on the anomeric carbon (the one involved in the bond that has lost its H) is DOWN (1).... now you look at the CH2OH on the other side of the O... (2) it's also pointed DOWN.

So, Beta.

I never knew this. This makes so much sense! Thanks a lot for posting this!