Structure and Spectroscopic Properties of p‐Benzoquinone Diazides

A series of p‐benzoquinone diazides were investigated by 13C‐NMR and IR spectroscopy as well as by semiempirical and abinitio calculations. In addition, X‐ray structure analyses of the parent compound and three derivatives were performed. The electronic structure and effects of substituents can be described in terms of diazoketo and diazonium phenolate resonance structures. While alkyl groups as substituents have only a minor influence on quinone diazides, electron‐withdrawing substituents lead to a larger participation of the aromatic diazonium phenolate structure. Benzoannellation, on the other hand, leads to a decrease of the interaction between the keto and diazo functional group and to properties more reminiscent of “ordinary” ketones and diazo compounds.