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Topic: Reaction  (Read 3413 times)

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Offline Serenagreene

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« on: December 05, 2007, 08:20:05 PM »
Is this reaction possible or likely?

Thanks,

-Serena

Offline RBF

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Re: Reaction
« Reply #1 on: December 05, 2007, 09:28:07 PM »
Not likely, since you have an acetal structure within the molecule.  Acetals are unstable to acid. The acetal oxygen is a much better leaving group under the conditions than the primary alcohol.

Offline Serenagreene

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Re: Reaction
« Reply #2 on: December 05, 2007, 09:35:43 PM »
So what would the resulting molecule(s) look like?  Would I end up with 2 H2Os + propane + n-propanol?

Offline RBF

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Re: Reaction
« Reply #3 on: December 05, 2007, 09:51:46 PM »
In the presence of any water, you are likely to end up with acetone and the triol (the acetal O's become OH groups).  The protection of ketones as acetals is common.  To regenerate the ketone, the acetal is hydrolyzed with water under acid conditions.
I'm not certain of the exact conditions in your reaction (what acid and the amount of water present).  Any nucleophilic solvent is likely to displace the acetal oxygens.

Offline Serenagreene

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Re: Reaction
« Reply #4 on: December 05, 2007, 10:56:39 PM »
Actually I had a mixture of molecules (this is for ORG STRUCTURE ELUCID or legal chemistry hazing).  We were told that we should 1st try to extract them. 
1 - dissolved mixture (was a liquid) in hexane:ethylacetate
2 - Aq (1) layer - first compound went into - salted out and used ether/pentane to get mostly pure compound.
3 - Org (1) layer  added 10% HCl
4 - Aq (2) layer - amine - added NaOH and then hexane:ethyl acetate to recover very very pure amine.
5 - Org (2) layer - added 10% NaHCO3
6 - Nothing in Org (3) layer
7 - Aq (3) layer added 10% HCl and ether/pentane - tried to rotovap, but compound disappeared.  Check a small sample against the original unknown mixture and the spot for this compound had become more polar.

I tried a column, 1st column the MP compound contaminated the whole thing.  2nd time I extracted the MP first, but then the amine didn't want to let go of the 3rd compound (used dichloromethane as my solvent until the amine was off (or I thought it was all off) and then switched to ether.  Most of the 3rd compound still came off with the amine.. and there was still a touch of amine in my H NMR and something weird....

Sigh, so I'm trying to figure out what the third compound is (not UV active, but stains with both p-Anisaldehyde and Potassium Permanganate).  Today I was told that it had a MW of 132 and based on a bad H NMR I subtracted the peaks that belong to the amine and ether (guess I didn't get it all off) I came up with this structure.  So in my lab report I'm trying to make sure I have some support for this structure and the problem I had with it.

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