Studies on tautomerism V: Some remarks on the tautomeric equilibrium, dimerization, and ionization of quinone monoximes (nitrosophenols)

Abstract

Abstract Measurements of absorption spectra in the ultra‐violet as well as in the visible (red) region were used to study the tautomeric equilibria in the case of p‐benzoquinone monoxime, 3‐chlorobenzoquinone‐4‐monoxime, naphthoquinone monoxime, and anthraquinone monoxime. In die case of the benzoquinone monoxime ‐ and less easily also with the chloroquinone monoxime ‐ the presence of the nitrosophenol form could be traced and its amount could be estimated. This was not possible with the naphthoquinone monoxime and the anthraquinone monoxime, which in solution seem to consist almost completely of the quinonoid form. A short theoretical comment is given. Experimental results and conclusions concerning the spectra of nitroso‐benzenes in general are discussed. Complications that may be caused by dimerization phenomena and by electrolytic dissociation of the compounds investigated were studied. Some nitrosophenols were found to be rapidly etherified at room temperature in methanol (and less quickly also in other alcohols) which had been acidified by addition of a few per cent, of concentrated hydrochloric acid.