sandozscientist8
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Need help with process interpretation - fatty acid amide synth
I have been working on preforming this reaction for a few weeks now and I am trying to understand the sequence in which to preform the following..I am
attempting to follow the protocol outlined in this paper and I have reached on point where the interpretation of the procedure is a bit fumbling..I am
trying to figure out what part of the reaction needs to be carried out over KOH. Every other part of this i understand and am familiar with, however
I have attempted to saturate my monoethanolamine prior to distillation for reaction prep, but i feel like this isnt right...However it might make
sense that I would need to de-protonate the ethanolamine prior to reaction...Any suggestions or feedback would be most helpful. Here is the excerpt
from which my confusion is derived...
"A mixture of fatty acid ethyl ester (6.56g) was treated with freshly distilled monoethanolamine (over KOH, 6.53g, 1:5 mole ratio) and trifluoroacetic
acid (10 ul).
Any advise to the order / method / ratios of KOH employed here would be great. I have also attached a link to the article below.
http://www.google.com/url?sa=t&rct=j&q=synthesis%20o...
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Lambda-Eyde
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It's used as a dessicant... Edit: in the distillation
[Edited on 19-6-2013 by Lambda-Eyde]
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sandozscientist8
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This was my intuition as well, the only thing that made me believe otherwise was that the KOH dissolved completely into solution when i was distilling
and *it appeared* that there was some carry over in my distillate. I cannot positively confirm this, and since the bp is far far higher for KOH, one
would be led to believe otherwise...
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paw_20
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KOH won't distill over to any great degree; similar to purification of water by distillation, salts and such will be left behind, although you should
leave the last 5-10% of fluid in the distilling flask. You can always check pH though (pKa of monoethanolamine is 9.5).
Also, as your reaction is acid-catalyzed, I'm not sure where you get the idea that monoethanolamine should be deprotonated.
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Shikimol69
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To carry-over KOH in your distillate, you may have experienced some bumping or foaming that is likely to happen with polar compounds such as TEA. You
have to apply heating and vacuum with carefulness, and place some trap on your distillation apparatus...
Edit: I forget, in a first place magnetic stirring or boiling stones should make the deal 
[Edited on 20-6-2013 by Shikimol69]
[Edited on 20-6-2013 by Shikimol69]
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sandozscientist8
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For some reason, even leaving 20-30% of the mixture in the distilling flask I am ending up with a distillate with a ph of 13.7....Is there an
agreeable amount of desiccant to use under such circumstances? I have been using aprx. 10 g. / 100 ml of ethanolamine.
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Shikimol69
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What makes you think your distillate contains KOH? At first glance, the pH that you give does not seem aberant, and since you measured it why don't
you do the ad hoc calculations to determine the purity of your amine before assuming the presence of desiccant? Your approach does not look very
consistent ...
[Edited on 21-6-2013 by Shikimol69]
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sandozscientist8
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I was led to this impression because of two major factors..The ph of my distillate was about 18% higher than it was prior to distillation. Also I
noticed striations in my distillate once it was able to settle without being disturbed for about 10 minutes. I could swirl the flask and it the
solution would become homogeneous.
Apologies for lack of preliminary work. Could you possibly direct me to a source of more information for obtaining formulas / further explanation ?
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