酸性雨モデルとしての希硝酸によるアゾ染料の異常退色

概要

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Decolorization of azo dyes by dilute nitric acid as acid rain model was pursued spectrophotometrically at 30℃. In the reaction of 4-arylazo-1-naphthols or 4-arylazoaniline, an induction period and then an increase in the rate were observed. Quantitative analysis of nitrogen dioxide by the Jacobs' method showed that the concentration of nitrogen dioxide increased remarkably as the decolorization reaction proceeded. The addition of a catalytic amount of sodium nitrite (source of nitrogen dioxide) to the dye-dilute nitric acid solution caused enhanced decolorization. Furthermore, 2,4-dinitro-1-naphthol (19% yield), 1,4-naphthoquinone (19% yield), and aryl diazonium salt (89% yield) were identified as main decomposition products of 4-arylazo-1-naphthols. From these results, the mechanism for the abnormal decolorization reaction was elucidated from autocatalyzed reactions by nitrogen dioxide as follows: (1) nitroso-dediazotization by nitrogen dioxide, (2) oxidation of the nitroso compounds by nitric acid, and regeneration of nitrogen dioxide.
武庫川女子大学の論文