ミロン呈色反応の機構に関する研究

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The mechanism of the Millon reaction with p-cresol was investigated using the Hopkins-Cole reagent. As shown in Fig.1, typical coloration was obtained with higher concentration of mercuric sulfate. 2-Chloromercuri-4-methylphenol(I), an assumed intermediate, colored blood red immediately on the treatment with sodium nitrite in sulfuric acid, and from the reaction mixture, brownish prisms(Pig. I, d. p. 172°C) were obtained. From the color reaction mixture of p-cresol, besides Pig. I, dark reddish violet prisms (Pig. II) and brownish red powders(Pig. III) were isolated. The constitutions of Pig. I were confirmed to be I and 2-nitroso-4-methylphenol(II) and those of Pig. II were II and mercuric ion. The structure of Pig. I was determined as formula III by X-ray diffraction studies, consequently, Pig. II was assumed as formula IV. These results indicate that the Millon reaction proceeds through the mercuration at the o-position of phenolic hydroxyl group, which is followed by the substitution of the mercury atom by attacking NO+, and the coordination of resulted nitrosophenol to either organic or inorganic mercury gives colored substances. Among 70 kinds of phenols tested, not only 2, 6 and 3, 5- but also 2, 5-disubstituted phenols, poly phenols, aminophenols and nitrophenols were found inactive or scarcely reactive. In the case of m-xylenol, such inactivity was proved to be caused by the steric hindrance of its methyl groups.