E1 reaction intermediate question (kaplan FL4, BS Q33)

[ihatebluescrubs]

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I thought that in an E1 reaction (unimolecular elimination), an carbocation ion forms when the leaving group leaves. However, this question states that E1cb (i think it still is talking about the same reaction?) states that an anion intermediate is formed instead.

Why is that?

Thanks!

 

[Jepstein30]

I thought that in an E1 reaction (unimolecular elimination), an carbocation ion forms when the leaving group leaves. However, this question states that E1cb (i think it still is talking about the same reaction?) states that an anion intermediate is formed instead.

Why is that?

Thanks!

Outside scope of MCAT but..

http://en.wikipedia.org/wiki/E1cB-elimination_reaction

e1cb is not same as e1.

Elimination is not tested on the MCAT, you should know the basics of e1 and e2 just in case but this is much more than would ever be necessary.