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Topic: Urgent urgent Help needed with elimination reactions?  (Read 2315 times)

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Offline theanonymous

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Urgent urgent Help needed with elimination reactions?
« on: October 29, 2012, 03:59:24 PM »


So for the first reaction, usually when I get a problem like this, he molecule is being treated with something like H-Br, so that tI can first protinate the OH on the alcohol, and then do the rest no problem... However, this one looks more compliacted with the "EtO-/EtOH" thing at the top of the arrow.

I don't know what to do first! *delete me*!!
« Last Edit: October 29, 2012, 04:24:18 PM by theanonymous »

Offline Babcock_Hall

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Re: Urgent urgent Help needed with elimination reactions?
« Reply #1 on: October 29, 2012, 06:51:47 PM »
Use the base to remove a proton from your alkyl bromide.

Offline Dan

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Re: Urgent urgent Help needed with elimination reactions?
« Reply #2 on: October 30, 2012, 04:01:47 AM »
Hint: You will have to draw these molecules in boat chair configurations to understand the regioselectivity and rate differences.

Edit: Boat/chair mix-up corrected
« Last Edit: October 30, 2012, 11:07:20 AM by Dan »
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Offline mamid

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Re: Urgent urgent Help needed with elimination reactions?
« Reply #3 on: October 30, 2012, 11:03:16 AM »
Draw the structures in CHAIR configuration so that both bromine and the anti-H on the neighbouring C('s) are axial (conformation necessary for concerted elimination). What (how many) conformations are possible in each case?

Offline orgopete

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Re: Urgent urgent Help needed with elimination reactions?
« Reply #4 on: October 31, 2012, 06:03:18 PM »
Hint, since eliminations are fastest when the groups are anti. For a ring, the leaving group should be axial. Draw the conformers with axial bromine atoms, and compare which protons are anti.
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