S and r rotation

[dray5150]

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Does anybody have any links to good 3 D stereochem sites on the web?I'm just having trouble visualizing R and S when I have to rotate it mentally.

 

[RPedigo]

Take a read through this thread-- it explains how you can get R and S configurations without rotating anything in your head. There's a special switch trick you can use. Hope this helps! LINK.

 

[170559]

Also look at this thread: http://forums.studentdoctor.net/showthread.php?t=554875

The picture worked for me, I would imagine a hugh 3D model hanging in front of me and I walk to the lowest priority sub and looking from there do the S or R assignment.

 

[dray5150]

Thanks man. So basically just ignore H (or the lowest priority group) and determine R and S rotation. If H ( or the lowest priority atom) is coming out of the page then reverse your answer. If it is going into the page then your original choice is right.

I've tried it on two problems and seem to have gotten it correct.

 

[TieuBachHo]

Thanks man. So basically just ignore H (or the lowest priority group) and determine R and S rotation. If H ( or the lowest priority atom) is coming out of the page then reverse your answer. If it is going into the page then your original choice is right.

I've tried it on two problems and seem to have gotten it correct.

Well, it's not always the case when you are dealing with R and S. Sometimes you need to see it sideways as well. And some molecules don't even have H as a substituent. H only represents the lowest substituent as in most of the cases. The more you practice the better you are at it. Train your brain to visualize its orientation in space. Just follow the rules.