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Topic: Multi-Step Synthesis  (Read 5901 times)

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Offline zebes

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Multi-Step Synthesis
« on: March 04, 2010, 11:04:13 PM »
I have a multi-step synthesis practice problem dealing with carbonyl chemistry. Any advise would be appreciated.

I have attached an image file of the final reaction and I need to make the mechanism. Sorry for the poor quality.

I know I have to use AlCl3 to add the reagent to the benzene ring. At one point I assume I will also have to add an organometallic compound.

Thanks.

I can also use the starting materials as often as I need to.
« Last Edit: March 04, 2010, 11:35:16 PM by zebes »

Offline Schrödinger

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Re: Multi-Step Synthesis
« Reply #1 on: March 04, 2010, 11:49:43 PM »
I know I have to use AlCl3 to add the reagent to the benzene ring. At one point I assume I will also have to add an organometallic compound. 
Use your reagent to acylate the benzene (2 moles). Replace the C=O by CHBr (reduce it ,then use NBS).
Next, generate Grignard reagents from the brominated product.
Add the Grignard reagent(2 moles) to the acyl chloride. You have your final product.

This last step is what I'm unsure of. Someone please help me on this : When I add a Grignard reagent to an acyl chloride, the chlorine is first knocked off, but the C=O remains right?
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Offline nj_bartel

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Re: Multi-Step Synthesis
« Reply #2 on: March 05, 2010, 12:23:26 AM »
Schrodinger, the idea is to help people gain the ability to solve problems for themselves, not simply put the answer in front of them.

Offline zebes

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Re: Multi-Step Synthesis
« Reply #3 on: March 05, 2010, 12:25:40 AM »
So I believe I have the answer using a different way. My main question now is what is the best way to replace an OH with a BrMg organometallic?

Offline Schrödinger

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Re: Multi-Step Synthesis
« Reply #4 on: March 05, 2010, 12:31:37 AM »
I'm sorry, I was only trying to help...I guess I got a bit over-enthusiastic. Sorry again :(
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Offline nj_bartel

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Re: Multi-Step Synthesis
« Reply #5 on: March 05, 2010, 01:43:31 AM »
It's fine, it takes practice, I'm certainly not the best at it.

Zebes - it would depend on the exact compound, but you the conversion can't be direct, due to the incopmatibility of alcohols and grignards (acid/base reaction)

Offline Schrödinger

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Re: Multi-Step Synthesis
« Reply #6 on: March 05, 2010, 07:04:19 AM »
Zebes - it would depend on the exact compound, but you the conversion can't be direct, due to the incopmatibility of alcohols and grignards (acid/base reaction)
Yes. The conversion can't be direct, as nj_bartel has rightly pointed out. As a matter of fact, that the OH group reacts with Grignard reagent is used to determine the number of moles of hydroxyl groups in a compound tested positive for alcohol groups.
http://en.wikipedia.org/wiki/Zerewitinoff_determination
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