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DOI: 10.1039/A809358J (Paper) Reference Section for: Phys. Chem. Chem. Phys., 1999, 1, 833-837

Mechanism of hydride transfer reaction from 4-(dimethylamino)phenyl methane derivatives to 2,3-dichloro-5,6-dicyano-p-benzoquinone

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Shunzo Yamamoto, Tetsuo Sakurai, Liu Yingjin and Yoshimi Sueishi

Abstract

The kinetics of the hydride-transfer reactions from bis[4-(dimethylamino)phenyl] methane (MH2), bis[4-(dimethylamino)phenyl] methoxy methane (MHOMe), Leuco Malachite Green (MGH) and Leuco Crystal Violet (CVH) to 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) have been investigated spectrophotometrically by means of the stopped-flow technique. The negative activation enthalpies were obtained for the hydride-transfer reactions from MH2, MHOMe and MGH to DDQ in dichloromethane. These negative activation enthalpies suggest that the charge–transfer (CT) complexes are true intermediates in the hydride-transfer reactions from these donors to DDQ, as previously pointed out for MH2–DDQ system in trichloroethane. The formation of charge–transfer complexes between MH2, MHOMe, MGH and CVH and p-chloranil (CA) were observed in EPA (ethylether–pentane–ethanol) at low temperatures. The oxidation potential (Eox°) of MHOMe, MGH and CVH were estimated using the linear correlation between the CT transition energy and the Eox° value for the known CT complexes between CA and N,N-dimethylaniline derivatives. The rates were found to be correlated to the Eox° values of the donors.

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