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Author Topic: Diels-Alder Regiochemistry  (Read 583 times)

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Cooper

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Diels-Alder Regiochemistry
« on: March 04, 2013, 01:15:29 PM »

Hi,

So when you're working with something like 1,3-butadiene for the diene, do you say that the terminal methyl (carbon-4) is causing an inductive effect on the adjacent carbon ONLY and causing the neighboring carbon (so that's carbon-3) to have a partial negative charge? Or do you say that the methyl donates a lone pair to cause the terminal carbon (carbon-1) to have a partial negative charge? I am almost positive the first suggestion is correct.

Basically I am asking does the methyl (carbon-4) on 1,3-butadiene cause carbon-1 or carbon-3 to have the partial negative charge?

If what I said is true, then the reaction in my picture below doesn't work, right?

Thanks

EDIT: I heavily edited this post to try to make my question less confusing.
« Last Edit: March 04, 2013, 01:55:55 PM by Cooper »
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Cooper

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Re: Diels-Alder Regiochemistry
« Reply #1 on: March 04, 2013, 01:16:30 PM »

Here's the picture.
« Last Edit: March 04, 2013, 01:44:59 PM by Cooper »
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Cooper

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Re: Diels-Alder Regiochemistry
« Reply #2 on: March 04, 2013, 07:16:31 PM »

Hi,

So when you're working with something like 1,3-butadiene for the diene, do you say that the terminal methyl (carbon-4) is causing an inductive effect on the adjacent carbon ONLY and causing the neighboring carbon (so that's carbon-3) to have a partial negative charge? Or do you say that the methyl donates a lone pair to cause the terminal carbon (carbon-1) to have a partial negative charge? I am almost positive the first suggestion is correct.

Basically I am asking does the methyl (carbon-4) on 1,3-butadiene cause carbon-1 or carbon-3 to have the partial negative charge?

Sorry, I meant to say 1,3-pentadiene, not butadiene. And the terminal carbon-5 would be causing induction effects. This thread is kind of a mess, so don't bother answering I will just ask my teacher tomorrow :P A mod can close it if you want.
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Re: Diels-Alder Regiochemistry
« Reply #3 on: March 05, 2013, 02:44:38 PM »

I don't know why there is an X over the reaction arrow. Although a methyl group is a weak electron donor, I would still expect the indicated regiochemistry to predominate. What has not been included is the stereochemistry of the three stereocenters.
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