The effect of electron-withdrawing substituents on the tautomerism between 1-aryl-3-methyltriazenes and 3-aryl-1-methyltriazenes

Abstract

Variable-temperature n.m.r. spectroscopic studies show that 1-aryl-3-methyltriazenes with strongly electron withdrawing para-substituents exist in a state of tautomeric equilibrium, ArNN·NHMe ⇌ ArNH·NNMe. Similar study of 3-methyl-1-p-tolyltriazene shows the presence of only the conjugated tautomer, p-MeC₆H₄·NN·NHMe, whereas arylmethyltriazenes with strongly electron-withdrawing ortho-substituents exist as the nonconjugated tautomer, ArNH·NNMe.