C. J. p. SPRUIT AND A. SPRUIT-VAN DER BURG 119 



Accordingly we have examined paraquinones derived from benzo- 

 furan, thianaphthene, selenanaphthene, and isoindazole. 



In the first place it was found that the properties of the pyrazole 



230 310 390 m^ 230 310 390 470 550 ftyj 



Fig. 13. Alterations of the nucleus. Similarity between the absorption spectra of 



isoindazolequinones and of analogous naphthoquinones. Left: isoin- 



dazole-4,7-quinone, 1,4-naphthoquinone. Right: alkaline solu- 

 tion of 2-hydroxynaphthoquinone, alkaline solution of 5-hydroxyisoin- 



dazolequinone. 



nucleus are very close to those of the benzene ring, as the absorption 

 spectra of the isoindazolequinones 



O 



