Determining R/S on a Fischer Projection

by James

 

{ 4 comments… read them below or add one }

M. Sankombo June 7, 2013 at 1:51 am

thank you soo much. this has been extremely helpful

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E Blake June 16, 2013 at 11:07 am

Hi! Can you please explain, if there is a longer chain, eg 3 stereocentres, how do you know for the middle stereocentre how to draw it in 3d? Which way is ‘up’ (flat on the page) and which way would be ‘down) (ie going behind us)

Hope that makes sense, thanks!

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james June 19, 2013 at 8:59 pm

Always for a Fischer, the groups pointing on the side are coming out of the page. That’s all the information you need to figure out R/S. As far as drawing in 3D, if you have that information, it’s probably best to redraw the molecule in “zigzag” formation and then use the R/S information to draw in the stereocenters that way.

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Ray June 30, 2013 at 9:02 pm

If the highest priority substituent is going into the page(dashed line) do you flip from R to S/vice versa?

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