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Urea is a typical amide. One of the most
characteristic reactions is the formation of salts with mineral
and organic acids.
Concentrated urea solution is divided into two test
tubes.
In the first test tube add 2-3 cm of concentrated urea
solution, add 2-3 cm of concentrated solution of nitric acid.
The contents of the test tube shake and cool. After cooling
the reaction mixture, precipitate - ureanitrate:

H N C NH + HNO H N C NH HNO

2 2 3 2 2 3

O O n .

Add 0,5-1 g oxalate acid to the second test tube. Ureid
precipitate (sour and medium, or cyclic composition):

H 2 N C NH + HNO 3 H 2 N C NH HNO 3
2
2
O O
n .

H
N H NH C O
H O C O
O C + O C + 2H O
2
H O C O
H NH C O
N
H

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