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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: rleung on November 05, 2005, 04:48:22 PM

Title: E1 rearrangement
Post by: rleung on November 05, 2005, 04:48:22 PM

Hey,

I have a question about the reaction of sulfuric acid with 4-methyl-2-pentanol.  Would there only be two products, the first and major product being 4-methyl-2-pentene and the second, minor product being 4-methyl-1-pentene?  Thanks.

Ryan

Title: Re:E1 rearrangement
Post by: movies on November 06, 2005, 12:45:57 PM

One of them will be highly favored because these types of dehydrations are under thermodynamic control.

By the way, this is an E1 elimination.  Rearrangements are different.

Title: Re:E1 rearrangement
Post by: FeLiXe on November 06, 2005, 01:55:16 PM

Wagner-Meerwein rearrangement only works if you have a methyl group right next to the carbenium ion. And the resulting ion should be more stable. 3,3-Dimethyl-pentan-2-ol could rearrange if you dehydrate it.

Title: Re:E1 rearrangement
Post by: rleung on November 07, 2005, 09:59:38 AM

But the possibilities I listed should be the only ones, right?  As in, did I miss any?  Thanks.

Title: Re:E1 rearrangement
Post by: movies on November 07, 2005, 05:59:58 PM

Structurally, yes.  There is the possibility of cis/trans stereoisomers with one of them though.

Title: Re:E1 rearrangement
Post by: rleung on November 08, 2005, 07:47:38 PM

Hmm, actually, my teacher is now saying that the dehydration of 4-methyl-2-pentanol gives a mixture of 5 isomeric alkenes, but I only count 3 (4-methyl-1-pentene, (E)-4-methyl-2-pentene, and (Z)-4-methyl-1-pentene).  Am I missing something?  Thanks.

Ryan

Title: Re:E1 rearrangement
Post by: movies on November 08, 2005, 11:29:49 PM

Ah, I see.  I think once you figure out the answer to your question in the other thread, you will see the answer to this one as well.