D-Ribose

[HopefulOncoDoc]

---

Members do not see this ad.

Sorry I made the mistake of titling it D-Ribose when it is actually D-Fructose. Could someone please explain to me how to determine whether the penultimate carbon (C5) is D or L? When I was converting this to the fischer projection, I looked at C5 and figured since the -H is down the -OH must be up and thus would be Left on the fischer projection making it L-Ribose, but it is actually D-Ribose. Could someone explain why my reasoning is incorrect? Thanks!

 

[PiBond]

I don't think i've ever seen an L isomer represented in a hawthorne projection--by convention (i believe) they're D. The penultimate hydroxyl nucleophilically attacks our carbonyl carbon so I don't think we'd be able to tell whether it was L or D because the oxygen bond to the carbon would look the same.

someone correct me if i'm wrong...

 

[lmarina1]

.

 

[HopefulOncoDoc]

Thanks guys that helps a lot. I just got a little confused in determining D or L from Haworthorne projection because in one of the questions on TPR Ochem, they asked to determine the confiduration a hawthorne projection so yea. But thanks again guys.