June 13, 2021, 11:03:15 AM
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Topic: Recovery of a hydrophobic product from Dowex-50  (Read 138 times)

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Offline Babcock_Hall

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Recovery of a hydrophobic product from Dowex-50
« on: June 11, 2021, 03:10:34 PM »
We are synthesizing two amino acids via a multistep synthesis, one has a methyl group and the other has a benzyl group.  We purified the amino acid with the methyl group using Dowex-50 and eluting the amino acid with 3 column volumes of 4 M HCl.  We saw adequate recovery and an increase in purity as judged by NMR.  For the compound with a benzyl group we tried 6 column volumes of 2 M HCl.  The very preliminary indication is that we obtained poor recovery.  This was not unexpected inasmuch as there are indications that Dowex like hydrophobic molecules.  IIRC we have tried ethanolic hydrochloric acid in the past, but we did not see much recovery.  What else should we try to recovery as much material as possible from this column?

Offline Babcock_Hall

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Re: Recovery of a hydrophobic product from Dowex-50
« Reply #1 on: Yesterday at 08:46:28 AM »
We continued to elute with a second portion of 2 M HCl, and we obtained a solid material, and I took a third fraction using 4 M HCl.  We are in the process of characterizing the various fractions.
« Last Edit: Yesterday at 09:08:06 AM by Babcock_Hall »

Online rolnor

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Re: Recovery of a hydrophobic product from Dowex-50
« Reply #2 on: Yesterday at 02:13:38 PM »
What is the benzylgroup, ester? Is sounds harsch with strong HCl with ester.

Offline Babcock_Hall

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Re: Recovery of a hydrophobic product from Dowex-50
« Reply #3 on: Yesterday at 02:53:12 PM »
The benzyl group is on the sulfur atom of a vinyl sulfone.  We chose HCl over 2 M ammonia to elute our compound.

Online rolnor

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Re: Recovery of a hydrophobic product from Dowex-50
« Reply #4 on: Yesterday at 04:36:16 PM »
Sulfides are usually stable to acid compared to ether or ester but still its not nice for the product. I am not so used to ion excange resins, can you use amberlite with carboxy residues, then you could use weaker acid maybe 0.1% TFA or something? I guess you have to evaporate significant volumes 2-4M HCl also, not very good.

Offline Babcock_Hall

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Re: Recovery of a hydrophobic product from Dowex-50
« Reply #5 on: Today at 09:05:32 AM »
Dowex-1 in the acetate form is another option for us.  It has been some time since I used it, but IIRC either HCl or HOAc can be used to elute one's compound.  I will look into this further.  The sulfur is part of a sulfone, as opposed to a sulfide.

Online rolnor

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Re: Recovery of a hydrophobic product from Dowex-50
« Reply #6 on: Today at 10:57:51 AM »
Sorry, sulfone. I guess they are even more stable.

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