392 PHYSIOLOGICAL CHEMISTRY. 



benzol, C 6 H 5 .C 3 H 7 (NENCKI and GIACOSA), also many other bodies 

 are oxidized into benzoic acid. If the side chain has several mem- 

 bers, the behavior is somewhat different. Phenol-acetic acid, C 6 H 5 . 

 CH 2 .COOH, in which only one carbon atom exists between the 

 benzol nucleus and the carboxyl, is not oxidized, but is eliminated 

 after coupling with glycocoll as plienaceturic acid (SALKOWSKI). 

 Phenyl-propionic acid, C 6 H 5 .CH 2 .CH 2 .COOH, with two carbon atoms 

 between the benzol nucleus and the carboxyl is, on the contrary, 

 oxidized into benzoic acid. Aromatic amido-acids with three car- 

 bon atoms in the side chain, and where the NH 2 group is bound to 

 the middle one, as in ty rosin, ar-oxyphenylamido-propionic acid, 

 C 6 H i (OH).CH 2 .OH(NH 2 ).COOH, and a-plienylamido-propionic acid, 

 C 6 H 5 .CH 2 .CH(NH 2 ).COOH, seem to be in great part burnt within 

 the body (ScHOTTEN" and BAUMAKN"). Phenylamido-acetic acid, 

 which has only two carbon atoms in the side chain, C 6 H 5 .CH(NH 2 ). 

 COOH, acts otherwise, passing into mandelic acid, phenyl-glycolic 

 acid, C 6 H 5 .CH(OH).COOH (SCHOTTEN). 



If several side chains are present in the benzol nucleus, then 

 only one is always oxidized into carboxyl. Thus xylol, C 6 H 4 (CH 3 ) 2 , 

 is oxidized into toluic acid, C 6 H 4 (CH 3 )COOH (SCHULTZEN* and 

 NAUKYH), mesitylen, C 6 H3(CH 3 )3 , into mesitylenic acid, C 6 H 3 (CH 3 ) 2 . 

 COOH (L. NENCKI), and cymol into cumic acid (M. NENCKI and 

 ZIEGLER). 



Syntheses of aromatic substances with other atomic groups 

 occur frequently. To these syntheses belongs, in the first rank, 

 the coupling of benzoic acid with glycocoll to form Jiippuric 

 acid, first discovered by WOHLER. All the numerous aromatic sub- 

 stances which are converted into benzoic acid in the body are 

 voided as hippuric acid. This statement is not true for all classes 

 of animals. According to the observations of JAFFE, benzoic acid 

 does not pass into hippuric acid in birds, but into another more 

 nitrogenized acid, ornithuric acid, C 19 H 20 N 2 4 . This acid yields as 

 splitting products, besides benzoic acid, a basic body, ornithin (see 

 page 389). Oxybenzoic acids (salicylic acid passes partly into sali- 

 cyluric acid) and the substituted benzoic acids form pairs with 

 glycocoll corresponding to hippuric acid, but also with the above- 

 mentioned acids, toluic, mesitylenic, cumic, and phenyl-acetic acid. 



