Fischer Projection to Wedge/Dash 6-Phosphogluconate Question

[betterfuture]

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Anybody know how to convert Fischer to wedge/dash. I can't follow through on how you determine what goes which way. Thank you.

 

[betterfuture]

And does anybody know for a wedge and dash diagram, where do you locate you eye to figure out which substituents go on horizontal on fischer and on vertical of fischer?

 

[theonlytycrane]

The answer choices only have 5 carbons 😵

 

[betterfuture]

Haha. Oh man! I didn't even catch that! Now, I am beyond just confused.

 

[theonlytycrane]

Is (a) the given answer?

 

[betterfuture]

Yes, it is.

 

[FutureD0C17]

There should be a 6th carbon but it doesn't matter in this case since the stereochemistry would be the same. We're looking for R and S configurations at each of the carbons and any OH on the right side of a fischer sugar takes the R form. You have to go through the fischer and match up the configuration to the dash/wedge

 

[betterfuture]

So for any sugar, if the OH is on the right side, it always takes the R form?

 

[theonlytycrane]

This might be a longer way, but I would figure out R/S on the carbons in the fischer projection and then R/S on the carbons in the open chain forms and then match them up- using any techniques of elimination such as different carbon lengths.

 

[BerkReviewTeach]

There should be a 6th carbon but it doesn't matter in this case since the stereochemistry would be the same.

Be careful with this reasoning, because if the sixth carbon were replaced with a phosphate group (as in this typo), the priorities on carbon 5 change, because OPO3 takes priority over OH while OH takes priority over C-6. The confirmation would actually change in this case.

 

[BerkReviewTeach]

The quick an dirty is that any "up" carbons (points sticking up in the backbone), the OH remains on the same side as the Fisher projection. Any "down" carbons (points sticking down in the backbone), the OH moves to the opposite side as the Fisher projection.