1961 年 81 巻 2 号 p. 231-235
In general, the indophenol reaction is thought to be positive in phenols only when there is a substituent in the position para to the hydroxyl group. However, recent reports have shown that the reaction becomes positive even when there is a substituent in the position para to the hydroxyl if such a substituent is liberated by this reaction. It was considered that the similar liberation of the para-substituent might also take place in the indophenol reaction using dimethyl-p-phenylenediamine as the reagent. In order to prove the liberation of such a substituent from the para-position, indophenol pigments were prepared from phenol and 2, 6-xylenol substituted in the para-position with halogen, carboxyl, or sulfonic acid. The pigments were examined by paper chromatography, ultraviolet and infrared absorption spectra, and elemental analysis, and they were all found to be entirely identical with those chemically synthesized from phenol and 2, 6-xylenol. It was thereby confirmed that these substituents present in the position para to the hydroxyl are liberated by this reaction.