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Author: Subject: End result of urea heating
John paul III
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[*] posted on 12-9-2018 at 11:46
End result of urea heating


I have a quick question:
If you heat up urea it releases nh3 forming biuret, triuret and on. At what temperature do these reactions cease and you’re left with NH3 and CO?

[Edited on 12-9-2018 by John paul III]
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Swinfi2
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[*] posted on 12-9-2018 at 12:33


I think the main reaction happening here is urea turning into ammonium isocyanate then decomposition to ammonium and isocyanuric acid. Polymerisation is a side product that makes it a mess to do.

But I've yet to do it myself so i could easily be wrong.
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DraconicAcid
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[*] posted on 12-9-2018 at 21:53


I'm surprised that urea would turn into ammonium cyanate, since Wohler's famous reaction was the reverse- ammonium cyanate turning into urea when heated.

You can't have ammonium isocyanate; cyanate can only be "iso" when it's bonded to an organic group through the nitrogen. [OCN]- is cyanate. CH3-O-CN is methyl cyanate. CH3-N=C=O is methyl isocyanate.




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Loptr
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[*] posted on 13-9-2018 at 16:45


I thought heating urea would produce biuret?



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UC235
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[*] posted on 13-9-2018 at 17:49


Urea decomposition is complex and produces a number of products depending on the temperature. The attached paper shows the product distribution and discusses mechanisms.


Attachment: Urea Pyrolysis.pdf (265kB)
This file has been downloaded 129 times

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