soma
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Use of ammonium hydroxide in ammonolysis.
I understand that amino acid amides can be synthesized by dissolving the ester in alcohol and then bubbling in ammonia and letting it sit overnight.
Would there be any problems foreseen just using ammonium hydroxide (28%)?
I'm wondering if any companies sell ammonium methoxide - which would be simply ammonia dissolved in methanol. Or ammonium ethoxide? I didn't see any
listed after searching with google.
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UC235
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You're going to have a hell of a time getting the reaction products out of water, I suspect. Also, you may have miscibility issues for some amino
acids. It may, nonetheless, work. I've used ~20% aq. ammonia for ammonolysis of methyl salicylate with good results.
http://www.sigmaaldrich.com/catalog/product/sigald/499145
http://www.sigmaaldrich.com/catalog/product/aldrich/779423
http://www.sigmaaldrich.com/catalog/product/sigald/341428
I know aldrich is not that helpful of a link, but the stuff is out there.
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DJF90
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Methanolic ammonia does indeed exist and is commercially available as an approx 9M solution (saturated). "Ammonium hydroxide" and (especially)
"ammonium methoxide" are misnomers. Ammonia in dioxane is also available (1-2M) and I've used it to advantage on occassion.
Ammonolysis of esters will proceed with aqueous ammonia, but may require good stirring if immiscible. Some appropriate co-solvent (e.g. MeOH?) could
be used if necessary.
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Sigmatropic
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Aqueous ammonia may be employed as in the case of chloroacetamide (http://orgsyn.org/demo.aspx?prep=cv1p0153). As far as I understand it a cleaner reaction is to saturate a solution of your substrate in alcohol
with gaseous ammonia in the cold. This effectively suppresses the related saponification happening when water is present.
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soma
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One paper says to bubble ammonia into the reaction mix using acetone and dry ice to cool it. They're reacting 1 mmol of N-acetylcysteine ester. They
say to bubble the ammonia into 100%ethanol for 10 minutes - then add the NAC ester - and then bubble the ammonia for another 10 minutes.
If larger amounts of NAC ester are used, would the bubble time need to be increased?
Also, any suggestions for how to use ammonium hydroxide to produce the ammonia gas ?
Thanks.
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