Sciencemadness Discussion Board

Determining the configuration at a stereocenter

Costanza9 - 11-4-2010 at 15:05

Hey, i'm kind of confused on determining the configuration of the stereocenter labeled 6 in this molecule.



Would the hydrogen at the stereocenter 6 be on the wedge coming out of the plane?

[Edited on 11-4-2010 by Costanza9]

ziqquratu - 11-4-2010 at 15:49

Absolutely. It's the only bond not shown - the other three are all defined (into or in the plane of the "page") - so the remaining bond (out of the page) must bear the hydrogen. Likewise at C7, the hydrogen must be on the dashed bond, going into the page.

JohnWW - 11-4-2010 at 16:14

That molecule is reserpine, a tranquilizing drug. I understand that in most countries it can only be prescribed by specialist psychiatrists, and it is used to tranquilize psychotically and criminally insane patients in secure mental hospitals.

There is a better illustration of its structure, showing full configurations at all its 7 stereogenic centers (including the tertiary-amine N), in Morrison & Boyd's Organic Chemistry, 3rd (1973, page 1004) and 6th (1992/2002) Editions. I have uploaded both editions to my rapidshare.com premium account, and posted the links for them in the References section. On the center labeled 6 above, the -OCH3 appears to go into the plane of the page, and the H goes above the plane.

Costanza9 - 11-4-2010 at 17:04

I keep getting an S configuration for the stereocenter labeled 6, when It should be R.



Pomzazed - 11-4-2010 at 19:43


Costanza9 - 12-4-2010 at 05:46

Quote: Originally posted by Pomzazed  


Wow, that is awesome. Thank you so much!

ziqquratu - 12-4-2010 at 14:15

It's what I've been explaining to my students lately - the group with the lowest priority MUST be on the dashed bond, or you'll get the wrong answer. But, since there are only two possible answers, you can just switch your answer to the correct one!