Details

Autor(en) / Beteiligte

• Józsa, Éva
• Purgel, Mihály
• Bihari, Marianna
• Fehér, Péter Pál
• Sustyák, Gábor
• Várnagy, Balázs
• Kiss, Virág
• Ladó, Eszter
• sz, Katalin

Titel

Kinetic studies of hydroxyquinone formation from water soluble benzoquinonesElectronic supplementary information (ESI) available. See DOI: 10.1039/c3nj01274c

Erscheinungsjahr

2014-01

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The kinetics and mechanisms of the redox reactions between hydrogen peroxide and 1,4-benzoquinone, 2-methyl-1,4-benzoquinone, 2,6-dimethyl-1,4-benzoquinone, 2-chloro-1,4-benzoquinone and 2,6-dichloro-1,4-benzoquinone were studied in aqueous media using spectrophotometric monitoring. The formation and decay of a hydroxylated 1,4-benzoquinone was detected. The formation of the intermediate was first order with respect to the parent 1,4-benzoquinone and hydrogen peroxide, whereas inverse first order dependence was revealed with respect to the hydrogen ion. The decomposition reaction had two parallel pathways: one was first order with respect to the intermediate, while the other showed second-order dependence. The values of the rate constant measured for the formation step were successfully correlated with both the redox potentials of the substituted quinone-hydroquinone systems and the p K a values of the hydroxylated quinone derivatives. Therefore, electronic effects govern the reactivity of the quinones in this process. NMR and GC-MS measurements were carried out to identify the products in the system. Quantum mechanical calculations were also carried out in these systems. The kinetics of the reactions between 1,4-benzoquinones and hydrogen peroxide were studied. A systematic study of substituent effects revealed a Hammett-like correlation, where the rate of reaction is mainly determined by electronic effects.