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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: orgoquestionmcat on October 11, 2021, 04:11:02 PM

Title: D vs L identification
Post by: orgoquestionmcat on October 11, 2021, 04:11:02 PM

Hello,

I'm studying a card, which I cannot interpret, don't know how to approach, or understand what the key takeaway is on this subject.
In what way is this figure resembling L-glyceraldehyde?

Thank you for your help.

Title: Re: D vs L identification
Post by: Babcock_Hall on October 11, 2021, 04:18:27 PM

Do you understand the basics of the D,L system of assigning configuration at a center of chirality?

Title: Re: D vs L identification
Post by: orgoquestionmcat on October 11, 2021, 04:55:16 PM

I think I'm missing some foundational rules.
According to the fischer projection, if NH2 is on the left, then it is L.
But I thought CH3 would be on the bottom, because the top carbon should be the #1 priority carbon, according to IUPAC rules.

What am I missing?

Title: Re: D vs L identification
Post by: Babcock_Hall on October 11, 2021, 07:14:23 PM

When assigning D and L configurations, the top carbon in the Fischer projection has the lowest IUPAC number on the top.  It is the number, not the priority, which is important.

Title: Re: D vs L identification
Post by: orgoquestionmcat on October 11, 2021, 09:12:39 PM

Thank you very much for your input! I fully understand now.

Title: Re: D vs L identification
Post by: rolnor on October 12, 2021, 05:05:32 AM

So, this is amphetamine, we should not discuss these things?

Title: Re: D vs L identification
Post by: Borek on October 12, 2021, 06:18:34 AM

We don't discuss recipes nor preparation details, nothing wrong with discussing some basic chemistry using amphetamine molecule as an example.