I am studying the reaction of carboxylic acids with a polymeric amine by enzymatic means. Is there a good method of determining quickly whether I have amide bonds or whether all that has happened is the formation of a primary ammonium-carboxylate salt? Regrettably I don't have easy access to HPLC-MS, but I have got FT-IR available. Would carboxylate peaks show up in the FT-IR spectrum, as the amide I and II bands do?
Also, can anyone tell me how susceptible the products might be to acid or alkaline hydrolysis?
Both carboxylate groups and carbonic acid groups should give signals (C=O stretching vibration, I believe) distinguisable from the amide I bands.
amide I: 1650-1700
carbonic acid: 1700-1725
carboxylic: 1550-1610
Anyway I would recommend measuring reference spectra of authentic samples of an amide (maybe chitin?) and a ammonium salt (maybe chitosan mixed with ammonium acetate?).
Brilliant, thanks. I'm planning to take spectra three pH values; at carboxyl pKa, and at one pH point above and one below. That would give different peaks if I have a salt, but no change if it's an amide. But I'll try your idea as well.
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