4-Phenyldiazenyl-substituted 3,6-di-tert-butylcatechol: synthesis and azo–hydrazone equilibrium

Reaction of 3-hydroxy-2,5-di-tert-butyl-1,4-benzoquinone with phenylhydrazine hydrochloride mainly leads to the corresponding hydrazone at the position 1 existing in tautomeric equilibrium with 3,6-di-tert-butyl-4-(phenyl- diazenyl)catechol. Thermodynamic parameters of the tautomerization were evaluated by NMR spectroscopy. The hydrazone structure was confirmed by XRD study.