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Author: Subject: Amide hydrolysis help
mnick12
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[*] posted on 18-3-2012 at 13:27
Amide hydrolysis help


I am a little embarrassed to ask a question like this, but I need some advice.

Lately I have been trying to hydrolyze small amounts of 2-aminobenzamide into 2-aminobenzoic acid, and I cannot get it to work! I find this very annoying since I have always been under the impression that amide hydrolysis was consider very simple. The first attempt was made refluxing stoichiometric amounts anthranilamide and aqueous HCl. After reacting for 2hrs the flask was cooled to just above freezing, and a large amount of crystalline solid was collected. This solid was not the original amide, since it refused to melt at the appropriate temp (113). However it wasn't 2-aminobenzoic acid either, since it would not melt at the correct tempurature (148).

My question is what is the best way to hydrolyze 2-aminobenzamide, and what could this mystery product be (perhaps 2-carbamoylanilium chloride?) ?

Again I know for the real chemists out there this probably seems like a stupid question, but I cannot figure it out!

Thanks!
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entropy51
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[*] posted on 18-3-2012 at 13:59


I am for sure not a real chemist, but I have been trying to be one long enough to know that nothing in chemistry is as simple as it seems.

I would try an excess of 70% sulfuric acid or 10% NaOH. I would probably try one or the other of them on a 1 gm scale before scaling up. I don't think this is a reaction that wants to be stoichiometric.
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mnick12
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[*] posted on 18-3-2012 at 21:21


entropy51 thank you for the advise.

Following your suggestion of aqueous NaOH, I tried a base catalyzed hydrolysis using 1.2 equivalents of potassium hydroxide. 100mmol of the amide was refluxed for 3hrs with 6.72g of KOH in 50ml of H2O. During the reaction large amount of ammonia was off gassed, indicating the decomposition of the amide. After cooling to almost 0C the dark red solution was neutralized with slightly less than 1 equivalent of H2SO4 ( to avoid protonation of the amine), and the solution precipitated a chalky light brown product. This material was collected by filtration and washed twice with 50ml of ice cold H2O. After drying a mp was taken (148C sharp) which confirmed a successful hydrolysis. I have not taken the mass of the final product, but it looks decent.

Thanks again.
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