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Topic: Organic synthesis  (Read 3147 times)

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Offline Squeak1107

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Organic synthesis
« on: May 06, 2016, 05:01:43 PM »
On question b attached I'm essentially trying to get from ethanol to propanoic acid and I'm having trouble adding in a carbon atom in the correct place.
My thought so far:
1) oxidise to aldehyde using acidified dichromate
2) use a gringard reagent MgBr-Me to add a carbon atom and then oxidise the resulting alcohol fully.

The obvious problem with my method is that the carbon atom ends up in the wrong place and you get proponone... However I can't think of a better way to add the carbon atom in. Any help to point me in the right direction would be very much appreciated!
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Offline Babcock_Hall

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Re: Organic synthesis
« Reply #1 on: May 06, 2016, 05:17:59 PM »
What about reversing the polarities of the 1-carbon and 2-carbon fragments from the polarities that you suggested?
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Offline Squeak1107

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Re: Organic synthesis
« Reply #2 on: May 06, 2016, 05:35:23 PM »
Quote from: Babcock_Hall on May 06, 2016, 05:17:59 PM
What about reversing the polarities of the 1-carbon and 2-carbon fragments from the polarities that you suggested?

I don't really understand what you mean by this, sorry!
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Offline Babcock_Hall

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Re: Organic synthesis
« Reply #3 on: May 06, 2016, 05:53:53 PM »
Your synthesis has a 1-carbon nucleophile and a 2-carbon electrophile.  What if you tried the opposite?
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Offline Squeak1107

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Re: Organic synthesis
« Reply #4 on: May 07, 2016, 08:43:12 AM »
I'm still not exactly sure how i would do that but Could I substitute the OH for OTs and the do a substitution reaction with CN-. This would then giving me CH2CH2CN which i could hydrolyse to the Carboxylic acid?
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Offline Dan

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Re: Organic synthesis
« Reply #5 on: May 07, 2016, 09:07:45 AM »
Quote from: Squeak1107 on May 07, 2016, 08:43:12 AM
I'm still not exactly sure how i would do that but Could I substitute the OH for OTs and the do a substitution reaction with CN-. This would then giving me CH2CH2CN which i could hydrolyse to the Carboxylic acid?

That's what I'd do.
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Offline Babcock_Hall

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Re: Organic synthesis
« Reply #6 on: May 07, 2016, 10:21:49 AM »
The other possibility is to turn ethanol into ethyl bromide then into a Grignard.  Then what could you do?
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Offline Squeak1107

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Re: Organic synthesis
« Reply #7 on: May 07, 2016, 02:32:42 PM »
Quote from: Babcock_Hall on May 07, 2016, 10:21:49 AM
The other possibility is to turn ethanol into ethyl bromide then into a Grignard.  Then what could you do?

Would you then react with Formaldehyde and oxidise to carboxylic acid?
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Offline Babcock_Hall

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Re: Organic synthesis
« Reply #8 on: May 07, 2016, 02:36:58 PM »
Why not just react the Grignard with carbon dioxide?
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