Beitrag zum Mechanismus der Kehrmannschen Phenoxazonsynthese

Abstract

Auf Grund kinetischer Untcrsuchuiigen wird versucht, den Bildungsmechanismus von 5H-Benzo[a]phenoxazon-(5) (4) naher zu beleuchten. -Bei der Reaktion zwischen o-Aminophenol (1) und 2-Hydroxy-naphthochinon-( 1.4) (2) entstehen 2-[2-Hydroxy-anilino]-naphthochinon-(1.4) (3) und 4. Fur diese Reaktion k t die Anwescnheit von Luftsauerstoff erfortlerlich; in inerter Atmosphare findet keine mefibare Umsetzung statt. Bei der Bildung in k h a n o l reagiert 3 nicht weiter. In Eisessig ist 3 gleichzeitig Zwischcnprodukt der Synthcse von 4, das teils durch intramolekulare Reaktion (kl : 4.25.10 6 sec -I ) , teils durch Reaktion mit o-Amino-phenol ( k~ = 5.07.10-2 Isec-1 Mol-1) entsteht. AuRerdem wird o-Aminophenol in einer Nebenreaktion ( k 3 : 1.32.10-4 sec-1) vom Losungsniittel acetyliert. ~ Diese Reaktionen verlaufen auch in inerter Atmosphare. Strdnskj, Katoutek, Stuikn und KrbeCkovdJahrg. 101 14'

Titrations in nonaqueous solvents

“…HC1 is a reasonably strong electrolyte (Kd = 1.1 X 10_2), and tetrazoles behave as weak bases. The data give the upper limit of the autoprotolysis constant of formic acid as 2.2 X 10-7. Acetic acid (26,96,124, H9, 205,250), acetic anhydride (27,81,142,149,198,240,272), or mixtures of these substances (163, 169,278) 167,169,198,240,272) or indicator (96,149 interferometric (263) and thermometric (262) methods have been reported for the titration of metal acetates or nitrogen bases in acetic acid. A variety of quaternary ammonium salts have been titrated in acetic acid using either indicator (88) or potentiometric (167) methods.…”

“…A series of oxazines (250) and aminoanthraquinones (149) (6) where values of a and b are characteristic of the indicator.…”

“…have been used as solvents for the determination of organic bases(26,27,81,96,108,142,167,240,250,272) or metal acetates…”

Solubilization of hydrophobic molecules in nanoparticles formed by polymer–surfactant interactions

“…It should be emphasized that the pH measured in all experiments was above 6.5, while the pK a of NIR [20] is between 6 and 7. It was found that at pH higher than 6.5 there is no change in emission intensity peak wavelength.…”

Functional group analysis

“…Oxazines have been investigated as indicators to be used in the titration of weak bases in nitromethane and in chloroform-dioxane mixture (217).…”