Fisher Projection Stereochemistry

[xatlasb]

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I always seem to get these problems wrong....

Can someone walk me through how to do this question?

Granted I couldn't take a screenshot of the entire question since it didn't fit on my screen, but I'd really appreciate it if you could go through and label with R and S for each of the stereocenters and how you got the answer.

Note: The correct answer is D, which is the one that got cut off. So was hoping you could properly label A, B, and C (they are given incorrectly on the question).

http://imageshack.us/photo/my-images/842/screenshot20130427at110.png/

 

[KyoPhan]

Hopefully you know the rule in assigning priority. If not, go ahead and take a look at this:
http://www.youtube.com/watch?v=NxIOrK6wF70
http://www.youtube.com/watch?v=4XaO_skZlus
Or look up any other place.

 

[xatlasb]

How come you are assigning the groups with the N as the highest priority for the top part of the Fisher projections? I thought that priority was assigned based on atomic number, and the last I checked, Carbon has a larger atomic number than Nitrogen?

 

[KyoPhan]

How come you are assigning the groups with the N as the highest priority for the top part of the Fisher projections? I thought that priority was assigned based on atomic number, and the last I checked, Carbon has a larger atomic number than Nitrogen?

You are correct in that you base it on the atomic number. However, Carbon is atomic # 6 while Nitrogen is atomic # 7!

 

[xatlasb]

Oh wow, I feel so stupid right now. Clearly I've been studying WAY too long for the night that I've forgotten my atomic number orders....

That's right, since N is more EN than C....

Okay, it's beditme.

Thanks again for the tutorial!! I'll definitely look at it again tomorrow morning when my brain is functioning at a higher level.

 

[KyoPhan]

If I remember correctly, they will give you the periodic table for the ochem section.