CHAPTER V 



NITROGENOUS COMPOUNDS 



(Amides) 



THE nitrogenous compounds found in plants and animals 

 apart from nitrates and ammonium salts which do not occur in 

 any considerable quantities may be broadly divided into two 

 principal groups, viz. proteins or albuminoids and amides. 

 The two groups are very closely allied. The distinction 

 between them is ultimately an arbitrary one ; but, in general, 

 the former are colloids and are coagulated by heat and by 

 various reagents, whereas the latter are crystalline and are 

 not so coagulated. The members of each group are derived 

 theoretically and, to some extent at least, actually, from those 

 of the other. They enter into the composition of all the 

 common foods to a greater or less extent, and play a prominent 

 and peculiar part in animal nutrition. Both groups include a 

 large number of different compounds and the majority are 

 very complex in character. 



Types. In general chemistry, the term " amide " is reserved 

 for compounds of the type of acetamide (CH 3 .CO.NH 2 ). 

 This, it will be seen, may be regarded either as acetic acid in 

 which the hydroxyl is replaced by NH 2 , or as ammonia (NH 3 ) 

 in which an atom of hydrogen is replaced by the acid radicle 

 (CH 3 CO). 



The acid radicles may, of course, be replaced by alcohol 

 radicles. The compounds so produced are generally called 

 amines. They are similar in many respects to the amides. 

 If ethylamine (CH 3 .CH 2 .NH 2 ) be taken as typical of the 

 amines, the essential difference between the two groups will be 

 recognised on comparison of the formulae. 



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