OChem question. Can someone clear this up for me?

[JCLewis90]

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Can someone explain the whole antiperiplanar/anticoplanar thing to me? I don't really understand what they are. And are they the same thing? What type of reactions require this?

Thanks!

 

[Riz0791]

The two words are interchangeable and are required for E2 reactions. For E2 reactions the beta hydrogen and the leaving group must be at a 180 degree dihedral angle, this conformation is called anitperiplanar.

 

[LazyP]

same thing! occurs during E2 reactions. taking a hydrogen, causing the alkene to be formed, will kick off the "anti" atom on the adjacent carbon. thus there must be a H in the anti coplanar spot for C=C to be formed in a E2 reaction.
http://science.uvu.edu/ochem/wp-content/images/A/antiperiplanar2.png

 

[JCLewis90]

Cool. thanks guys. So there is nothing like this for SN2, SN1, or E1 is there? Just making sure I've got everything covered.

 

[Hurkyules]

Yes, it's only for E2.