Radikalreaktionen an N‐Heterocyclen. V. EPR‐Untersuchungen von Nitroxid‐Radikalen substituierter 3‐Anilino‐1,5‐diphenyl‐pyrazole

Abstract

Radical Reactions of N‐Heterocyclic Compounds. V. ESR‐Investigation of Nitroxide Radicals of Substituted 3‐Anilino‐1,5‐diphenyl‐pyrazoles The correlation of the e.s.r. splitting constants with the Hammett values for nitroxides from substituted 3‐anilino‐1,5‐diphenylpyrazoles 1a – e and substituted 1,5‐diphenyl‐3‐p‐toluidino‐pyrazoles 1f – i provides evidence for extensive interannular conjugation between the N 1 ‐benzene ring and the pyrazole ring of these nitroxides. The conjugation between the arylamino group and the pyrazole ring is extensive only in the nitroxides derived from 1f – i . The captodative substituted p‐toluidino‐nitroxides 2g, h have a better spin distribution than the nitroxide 2i with two electron‐donating substituents.