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Topic: Hydrobromic acid in methanol reaction  (Read 6393 times)

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Offline Cooper

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Hydrobromic acid in methanol reaction
« on: November 08, 2012, 05:09:27 PM »
Hello,

I'm doing my homework and I'm stuck on this problem, I've tried it several times but am having trouble coming up with the right answer.

This is the problem,

3-methylbut-1-ene + HBr (in methanol) --> ?

My first thought (I've attached a paint file) was that the double bond acts as a nucleophile and attacks the proton from HBr, giving 2-methylbutane with a carbocation on the third carbon. Then a methyl shift would occur, but the resulting product would be the same.

Then I thought the oxygen on the methanol attacked as a nucleophile to the carbocation and produced 3-methanol-2-methylbutane. Then the bromide from the HBr in the beginning would act as a nucleophile and remove the proton from the methanol, giving the product. EDIT: Actually, technically another methanol would pluck off the proton, because it's a better nucleophile and more abundant, my bad.

That didn't work so I thought that maybe the HBr and methanol reacted together first?

Thanks for any help in advance!

~Cooper
~Cooper :)

Offline discodermolide

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Re: Hydrobromic acid in methanol reaction
« Reply #1 on: November 08, 2012, 05:18:21 PM »
Try a proton shift from the end of the molecule to the cation that you drew to give a tertiary cation, MeOH will then attack there to give 2-methoxy-2-methylbutane.

The drawing starts with the cation you drew.
« Last Edit: November 08, 2012, 05:28:52 PM by discodermolide »
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Offline Cooper

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Re: Hydrobromic acid in methanol reaction
« Reply #2 on: November 08, 2012, 05:34:11 PM »
Thank you! :D I should've seen that! And thanks for the drawing :) What did you use to make it? 

PS What do the snacks mean? If I give you one does that mean like a +1 comment? lol

~Cooper
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Offline discodermolide

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Re: Hydrobromic acid in methanol reaction
« Reply #3 on: November 08, 2012, 05:39:28 PM »
I used ChemDraw.
The snacks are there to register your like or dislike of the answer, if you think it helps give one . If you don't like the answer, or it is wrong take one away.
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Offline Cooper

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Re: Hydrobromic acid in methanol reaction
« Reply #4 on: November 08, 2012, 05:40:51 PM »
Oh okay I gave you one :P Thanks again :)

~Cooper
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Offline discodermolide

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Re: Hydrobromic acid in methanol reaction
« Reply #5 on: November 08, 2012, 05:42:49 PM »
My pleasure ;D
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