336 IMMUNOLOGY 



O 



HO— As— / N— r'NH7'+'0"'i=N— "OHTh"^— Cl= 



I ^ ^ ' ' 



OH 



O 



I' / \ 



HO— As— (^ y—N=N—Cl + 2H„0 



OH 



This p-aminobenzenearsonic diazoniuin chloride could react with 

 aromatic amino acids of the proteins replacing a hydrogen on the 

 nucleus, as was the case with the sulphonic acid derivatives. Using 

 tyrosine again as an illustration we have : 



O 



HO 



_/\ 



HO— As— / \ -N=N— r"ci"+ "h" 



OH H NH 



^^-^^ H H O 



H H 



I I II 

 — C— C— C— OH = 



HO— As— <^ \ — N=N— 



C— C— C— OH 



OH H NH^ 



Arsonic Protein Compounds. — The compound of protein and 

 the p-aminobenzenearsonic acid is a new antigen for which spe- 

 cific antibodies are produced. 



Aliphatic Side Chains Not Diazotizable. — When an amino 

 (-NHo) group is in the side chain of a compound, i.e., not at- 

 tached to a carbon atom in a benezene nucleus or ring, as in benzyl 



amine ^ y — CH^NH,, that amino group is in general not 



diazotizable, the reaction with nitrous and hydrochloric acids 

 under such conditions giving the corresponding alcohol, free 

 nitrogen (N2) and water. This may be shown as below, using 

 benzyl amine : 



