APPENDIX. 331 



CH, CH 3 



CO NH a CO ONH 



or 



H' 



(C 2 H 3 0) being the radical of acetic acid. 



Varieties. Several of the varieties of amides are represented in the 

 products with which we have to do. 



(a. ) Monamides which are derived from a monatomic acid that is to 

 say, an acid which contains the carboxyl group COOH, once, by the sub- 

 stitution of NH 2 for OH in this group. In these compounds if only one 

 is the II in NH 3 is replaced by an acid radical, a primary monamide of 

 formed; if two, by acid or alcohol radicals, a secondary monamide; if 

 three, by acid or alcohol radicals, a tertiary monamide. 



Two monamides are also formed from each diatomic acid (i.e., those 

 which contain OH twice, once in the carboxyl group COOH, and once in 

 the alcohol group C n H 2D OH), both by the substitution of NH 2 for OH, 

 and therefore having the same composition. They are isomeric and not 

 identical however, the one formed by the substitution of NH 2 for the alco- 

 holic OH being acid, while the other formed by the replacement of the 

 basic hydroxyl is neutral. The acid amides are called amic acids, or may 

 form a class by themselves, called alanines. 



Three amides are obtained from each diatomic and bibasic acid: (1.) 

 An acid amide or amic acid, derived from the acid ammonium salt by ab- 

 straction of one molecule of water. (2.) A neutral monamide (or imide), 

 derived by abstraction of two molecules of water from the ammonium 

 salts. (3.) A neutral amide or (b) DIAMIDE, derived from the ammonium 

 salt by abstraction of two molecules of water. Thus succinic acid gives: 



Succinamic Acid . . . C 2 H 4 -j 



Succinimide . . . . C 2 H 4 j j i NH 

 Succinamide . . . . C 2 H 4 (CO NH 2 ) 2 



(a) PEIMAKY MONAMIDES. 

 Glycin, glycocol or glycocin, or amido-acetic acid 



O.H.O.n c II O) 



H' > N or ^ Yr [ occurs in the body in combination, as in 



H' ) H *> 



the biliary acids, never free. Glycocholic acid, when treated with weak 

 acids, with alkalies, or with baryta water, splits up into cholic acid and 

 glycin, or amido-acetic acid. Thus: C 26 H 43 N0 6 -f- H,0 = C 2P H 40 6 

 + C 2 H 5 N0 2 . Glycocholic acid + water = cholic acid -f glycin, and 

 under similar circumstances Taurocholic acid splits up into cholic acid 

 and taurin: C 26 H 4& 3 NS0 7 + H 3 = C 26 H 40 6 + C 2 H 7 NS0 3 , or 

 amido-isethionic. Taurocholic acid -f- water = cholic acid and taurin. 

 Glycin occurs also in hippuric acid. It can be prepared from gelatin by 

 the action of acids or alkalies; it can also be obtained from hippuric acid. 



