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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Cheemistree8889 on April 22, 2007, 08:28:35 PM

Title: Ethyl rearrangement???
Post by: Cheemistree8889 on April 22, 2007, 08:28:35 PM

I cannot do this mechanism without a ethyl rearrangement...  The solvent is hydroxide and water.  I just don't understand how you can make that carbon tertiary without a ethyl rearrangement.

Title: Re: Ethyl rearrangement???
Post by: bigfluffyz on April 23, 2007, 03:53:46 AM

I have also been wroking on this problem I wasn't able to figure it out. I started out with an elimination making an enamine then I had a methyl shift. Then I  went through a highly unlikely sequence of hydride shifts (going from secondary to primary) which I can't see happening. Any help would be appreciated.

Title: Re: Ethyl rearrangement???
Post by: Dan on April 23, 2007, 07:57:29 AM

Hmmm. Here's a suggestion. I'm not totally convinced, but it's all I can think of right now.

If you go via an aziridinium(?) ion, which is then opened with hydroxide at the less hindered site, you get the right compound. However, you can open aziridines with HCl, so I think it might be a little bold to suggest this mechanism. I have to admit that I don't know all that much about aziridines, perhaps some of the experienced organic chemists here would care to criticise...

Title: Re: Ethyl rearrangement???
Post by: bigfluffyz on April 23, 2007, 10:08:00 AM

Thanks a bunch I never new that was a possibility.

Title: Re: Ethyl rearrangement???
Post by: Custos on April 23, 2007, 10:32:34 PM

Yes, it's a well known phenomonum called neighbouring group participation (http://en.wikipedia.org/wiki/Neighbouring_group_participation). It's common with nitrogen and sulfur, and is one of the reasons that mustard gas is so dangerous - it generates acid and an alkylating agent in the same place.