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Topic: 2 orgo questions  (Read 3113 times)

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Offline Kwu

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2 orgo questions
« on: October 10, 2013, 12:53:16 AM »
Hi, I need help with 2 questions



The first problem, I know the first molecule is very unstable but I need to know why the other molecule is more stable.

The second problme, I have no clue.

Help would be appreciated, thanks!
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Offline Archer

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Re: 2 orgo questions
« Reply #1 on: October 10, 2013, 02:28:57 AM »
Are these molecules planar as you have drawn them or do they adopt a different conformation?
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Offline Kwu

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Re: 2 orgo questions
« Reply #2 on: October 10, 2013, 02:56:15 AM »
It doesn't mention.
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Offline Dan

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Re: 2 orgo questions
« Reply #3 on: October 10, 2013, 03:03:18 AM »
Quote from: Kwu on October 10, 2013, 02:56:15 AM
It doesn't mention.

You will have to think then!

For the first one, try building models of both compounds. The answer should quickly become clear.

For the second one, you need to consider 3D structure of both compounds and also the stereoelectronic requirements of E2.
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Offline Kate

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Re: 2 orgo questions
« Reply #4 on: October 10, 2013, 08:44:04 AM »
For the 2nd question, the first molecule is more unstable (both bromines are cis), so it's more reactive towards E2, right?
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Offline Archer

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Re: 2 orgo questions
« Reply #5 on: October 10, 2013, 09:35:40 AM »
Quote from: Kate on October 10, 2013, 08:44:04 AM
For the 2nd question, the first molecule is more unstable (both bromines are cis), so it's more reactive towards E2, right?

There is only one Bromine on the molecule
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Offline Kate

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Re: 2 orgo questions
« Reply #6 on: October 10, 2013, 11:08:05 AM »
Quote from: Archer on October 10, 2013, 09:35:40 AM
There is only one Bromine on the molecule

OMG, you're right, I mistook the 2 methyls for 2 bromines. >:(

In an E2 reaction, the hydrogen being removed by the base has to be anti-periplanar to the halogen that leaves.

Is it because of steric effects between the base and the methyl? If the hydrogen being removed is in trans with the methyl, then the base can remove it faster?
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