Acidity Dependence of the Tautomeric Equilibrium Between the First Conjugated Acids of 4-Aminoazobenzenes

Abstract

Acidity functions based upon primary anilines which have no ortho substituents have been established in 20% ethanol-80% aqueous sulfuric acid solutions, and compared with those based upon o-substituted anilines and azobenzenes. It was found that the tautomeric equilibrium between azonium and anilinium forms in 4-aminoazobenzene derivatives invariably shifts to the azonium form with increase in acidity. This observation has been interpreted in terms of acidity functions.