AMINO-ACIDS, PROTEINS, UREA AND URIC ACID 99 



/(OC2H5 H)NH2 /NH2 



0C< + -^0C< +2C2H5OH 



\(OC2H5 H)NH2 ^NH2 



Di-ethyl carbonate Urea 



Also carbonyl chloride (phosgene), COCI2, yields urea with 



ammonia. 



H)NH2 /NH2 



C0(Cl2+ ->0C< 



H)NH2 ^NH2 



Carbonyl chloride Urea 



Thus the relationship of urea to both carbonic acid and formic 



acid is established. 



The most interesting synthesis of urea is one which shows 



little as to its constitution, but which is important because it 



was the first preparation, from purely inorganic substances, of 



a compound found in animals or plants. In 1828 the German 



chemist Wohler obtained urea by simply heating the inorganic 



salt ammonium cyanate. In this conversion no other substance 



was added or produced, there simply being a rearrangement of 



the atoms. 



/NH2 

 NH4O - CN -> 0C< 



Ammonium cyanate Urea 



Up to the time of this historic synthesis no substance known 

 only as a product of living organisms or, as they were termed, 

 vital products, had ever been prepared in the laboratory. 

 This caused the abandonment of the view that organic sub- 

 stances belonged to a different class, and needed the presence 

 of a different kind of chemical reaction than inorganic sub- 

 stances. The vital force, as it was called, was not essential 

 to the formation of organic compounds. This is not saying, 

 however, that living matter itself can be produced from non- 

 living matter. Wohler's synthesis of urea thus stands as an 

 epoch-making discovery, and marks the real beginning of a 

 new era in organic chemistry. 



