98 ORGANIC AGRICULTURAL CHEMISTRY 



This acid is not known as the free acid, but is known both in 

 the form of its ammonium salt and also of its ethyl ester. 



NH2 - COONH4 NH2 - COOC2H5 



Ammonium amino-formate Ethyl amino-formate 



Now when ammonium amino-formate is heated, water is lost 

 and urea results. Also when ethyl amino-formate is treated 

 with ammonia, urea is formed and ethyl alcohol is the other 

 product. These reactions leave no doubt as to the structure of 

 urea and its relation to formic acid. 



NH2 -CO(0)NH2(H2) -> NH2 -CO -NH2 + H2O 



Ammonium amino-formate Urea 



NH2 -CO(OC2H5+H)NH2 -> NH2 -CO -NH2 + HO -CsHg 



Ethyl amino-formate Urea Alcohol 



The relation of urea to carbonic acid is also shown by this first 

 synthesis above, for the ammonium amino-formate is produced 

 when carbon dioxide and ammonia are brought together. 



/NH2 

 C02 + 2NH3->C=0 



\ONH4 



Ammonium amino-formate 

 Ammonium carbamate 



As this compound in its relation to carbonic acid is both an acid 



amide and an ammonium salt, it is known also as ammonium 



carbamate. This with a molecule of water forms ammonium 



carbonate. 



/NH2 /ONH4 



C = O -f H2O -> C = O or (NH4)2C03 



\ONH4 \ONH4 



Ammoniimi carbamate Ammonium carbonate 



Carbonic acid though not existing free is known as its di-ethyl 



ester. 



/OC2H5 



0C< 



^0C2H5 



and this compound with ammonia forms urea and alcohol. 



