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Topic: How to Dry over KOH or P2O5  (Read 20447 times)

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Offline ID101

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How to Dry over KOH or P2O5
« on: June 14, 2010, 03:32:47 PM »
I am trying to dry a peptide resin during the Low-high TFMSA cleavage method.  How do I go about drying over KOH or P2O5?  Does the KOH/P2O5 get added to the peptide resin?  Or is it more like a dessicator setup, where the KOH or P2O5 is below the resin (separated)?  It is recommended that this procedure be done under vacuum. 

Thank you for your help.


Offline dunno260

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Re: How to Dry over KOH or P2O5
« Reply #1 on: June 16, 2010, 02:46:43 AM »
I would imagine its a desiccator type setup because otherwise you would have to remove the potassium hydroxide or phosphorus pentoxide from the resin prior to use somehow.  I would recommend putting your resin in some sort of appropriate bottle/vial whatnot and using a kimwipe secured with a rubber band to keep the stuff from leaving the bottle/vial as its drying or venting under vacuum.  Just use the KOH or some phosphorus pentoxide in a similar container (with P205 you won't need a ton and ideally should have it over as thin a layer as it tends to coat itself in a layer of phosphoric acid as it dries requiring that you change it out.

Offline jessetjenkins

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Re: How to Dry over KOH or P2O5
« Reply #2 on: June 12, 2011, 04:58:50 AM »
Thank You so much, Exactly the answer I needed. It just took some quick searching...Im gonna use a test tube containing the wet solid inside of a schlenk tube under N2 with some p205 in the bottom of it!

Offline jessetjenkins

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Re: How to Dry over KOH or P2O5
« Reply #3 on: June 12, 2011, 04:59:34 AM »
Oh, Oh and I shouldnt forget the kim wipe with rubber band on the test tube!!!

Offline jessetjenkins

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Re: How to Dry over KOH or P2O5
« Reply #4 on: June 13, 2011, 02:49:26 PM »
Axtually, it turns out the dessicator method is the easy way to go. I just put my product in a beaker and purged the dessicator with vacuum and nitrogen. Although, I'm not sure how long to leave the product in the dessicator... Do you know how long it usually takes.. There is some condensation on the top of the dessicator, perhaps solvent left over from the product? It is supposed to be a DMF salt.


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