Issue 11, 1978

Kinetics and mechanism of the acid deamination of N-substituted quinone di-imines measured with a multi-mixing, stopped-flow technique

Abstract

A stopped flow apparatus with six syringes and five mixing chambers is described which allows several stoppages at given intervals. Seven partially ring methylated, N-substituted p-phenylenediamines (R) were oxidised by iodine or permanganate. The deamination of the quinone di-imines (T+) formed was studied in the pH range 1–10 by means of a colour coupling process after different intervals or from the extinction of the radical intermediate as a function of time. T+ is in a fast equilibrium with its protonated form TH2+. Deamination is initiated by nucleophilic attack on the most positively charged carbon atom of the ring. Therefore, in acid solution TH2+ is deaminated by H2O giving the substituted quinone monoimine and in alkaline solution T+ is deaminated by OH, giving the respective unsubstituted quinone monoimine. The equilibria and the rate constants were measured at 25 °C. The stability maximum of T+ is at pH 6 whereas the N-substituted quinone monoimines are stable at pH <2. The further deamination of quinone monodimethylimine was studied between pH 1 and 10. Parallel reactions with OH and with H2O were found, giving in both cases p-benzoquinone

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 2, 1978, 1188-1193

Kinetics and mechanism of the acid deamination of N-substituted quinone di-imines measured with a multi-mixing, stopped-flow technique

U. Nickel, K. Kemnitz and W. Jaenicke, J. Chem. Soc., Perkin Trans. 2, 1978, 1188 DOI: 10.1039/P29780001188

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