Benzoquinone imines. Part V. Mechanism and kinetics of the reaction of p-benzoquinone monoimines with m-phenylenediamines
Corbett, John F.
Журнал:
Journal of the Chemical Society B: Physical Organic
Дата:
1969
Аннотация:
Oxidation of mixtures of p-aminophenol and m-phenylenediamines is shown to give aminoindoaniline dyes by a reaction between p-benzoquinone monoimine and the m-diamine. In the coupling reaction, the rate-controlling step involves, at pH > 8·5, electrophilic attack by the neutral monoimine on the neutral m-diamine and, at pH < 5, by the protonated monoimine on the neutral m-diamine. In the pH region 5â 8·5, both reactions make a significant contribution. The resulting leuco-indoaniline then undergoes rapid oxidation, by a second molecule of monoimine, to give the dye. The effect of C-methylation of the reactants on the rate of coupling is consistent with the suggested mechanism. Thus, C-methylation of the monoimine decreases the rate of coupling, while C-methylation of the m-diamine increases the rate.
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