Derivatization of Amines with 4‐Substitured 7‐Nitrobenzofurazans Electrophilc derivatives of 4‐nitro‐benzofurazan with different reactivities were used to synthesize 28 new mono‐ and disubstituted 4‐amino‐7‐nitrobenzofurazans 2b, 2d, 2f–2i, 2l, 2m–2n, 3b–3f, 3h–3j, 4e–4d, 4f–4k, 4m, 4o–4p. A reaction mechanism is proposed on the basis of the differences of the reactivities and a preliminary kinetic examination. The acid character of the NH‐function in monosubstituted compounds is demonstrated by means of spectroscopical investigation of pKa‐values. Data from i.r., u. v./vis, and fluorescence studies are offered.

UV‐VIS‐ and IR‐Spectroscopic Studies with N‐Substituted 4‐Amino‐7‐nitro‐benzofurazans Starting from spectra of parent substance benzofurazan the influence of different functional groups (NO2, OH, NH2, NHAlk, NAlk2, NHAr, NArAlk) in 4‐ and (or) 7‐position on the shape of spectra and the intensity of individual bands was examinated. It was tried to assign spectral bands to defined absorptions in the u.v./vis and i.r. range. The long‐wave band in the solution‐VIS‐spectra of N‐substituted 4‐amino‐7‐nitrobenzofurazans was identified as a charge‐transfer band. By the use of constants α, β, and π* by Kamlet and Taft the influence of different properties of solvents was correlated with band shifts in the UV/VIS range. A qualitative correlation was found between \documentclass{article}\pagestyle{empty}\begin{document}$ \bar \nu _{{\rm max}} $\end{document} of the long‐wave band in the VIS‐spectra, the polarographic half wave potential E 1/2 and the sum of polar substituent constants Σσ* of Taft. These proportions were plotted in a three‐dimensional diagram.

Electrochemical Reduction of 4‐Substituted 7‐Nitro‐benzo‐furazans The electrochemical properties of 4‐methoxy‐, hydroxy‐, alkylamino, and arylaminosubstituted 7‐nitrobenzofurazans (1a–1h) are studied between pH 1,7 and 11,6 by use of buffer solutions containing different portions of various organic solvents. Reduction waves which are present in polarograms, are well reproducible and practicable for qualitative and quantitative analysis of amines. A mechanism of reduction is suggested by reason of polarographic and coulometric results. The half wave potentials are correlated with various substituent constants. A value of ϱ = + 0,32 follows from the determination of the reaction constant from the slope of the E 1/2 – σp – relation for the polarographic reduction of each nitro‐function.

Die Titelverbindungen (I), (IV) bzw. (VII) werden durch Umsetzen mit den Aminen (II), (V) bzw. (VIII) unter variierenden Synthesebedingungen in die 28 neuen 4‐Aminoderivate (III), (VI) und (IX) übergeführt.

Die synthetisierten unsymmetrisch verbrückten Tetramethoxyderivate 2a–w wurden durch Ätherspaltung mit AICl3 oder AlBr3 in die entsprechenden tetravalenten Hydrochinone 3a–r übergeführt und diese zu den gelben Dichinonen 4a–P oder partiell zu den tieffarbigen intramolekularen Chinhydronen 6a–o oxidiert.