E2 reaction on DAT

[BRZ24]

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How crazy are the E2 reactions with the stereoselectivity?

I learned from chad's that if you are doing E2, you must grab a hydrogen that is positioned antiperiplanar from the leaving group and if there are two hydrogens that are antiperiplanar then you pick the most substituted carbon(zaitsev)

Now I stumbled upon this video that showed that you have to satisfy the zaitsev's rule first and then antiperiplanar thing by rotating the molecule OR draw the newman projection, etc.

wtf?? I didn't know you have to do that?

http://www.youtube.com/watch?v=O1qyWZEzmyI

I don't understand why he doesn't just grab the hydrogen from the methyl group on the top left corner since it has a hydrogen on a dash position and form the double bond between the carbon thats on the top left corner and the one bearing the br initially.

 

[Glimmer1991]

Personally, I wouldn't worry much about this at all. I think Chad covers it in enough detail. On my test, the answer choices weren't too tricky or anything... I think for an E2 reaction, the answer would not be too hard to pick out. If you've got the major concepts, the nitty gritty just isn't so important. 😉

 

[Dotoday]

You need to know E1 and E2 as well as Zaitsev versus Hoffman. As far as stereochemistry, just make a trans/E. Most substituted alkene when dong zaitzev. That is all. Hope it helps.

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