Kinetic studies of hydroxyquinone formation from water soluble benzoquinones

Abstract

Table of contents entryThe 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. 3 AbstractThe 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-bezoquinone and hydrogen peroxide, whereas inverse first order dependence was revealed with respect to 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 pK 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.4

A detailed kinetic study of the direct photooxidation of 2,4,6-trichlorophenol

“…S4 and S5 in the Supplementary information). The Uv-vis spectra of TCP [9,12,13], DCQ [9,12,13,23,24] and DCHB [23,24] are all available from the literature.…”

“…Each of these hydroquinone products can easily be oxidized to the corresponding quinone. This process is known to be reasonably fast under neutral conditions in the presence of oxygen [9,24]. Finally, the 2,6-dichloro-1,4-benzoquinone has a wellknown photoreaction, which produces a hydroxyquinone and the hydroquinone [23].…”

“…An interesting and unintuitive observation was also made during a kinetic study of the chemical oxidation of chlorophenols: the rate of reaction is influenced by light, even if it is in the visible range [8]. The reason for this phenomenon was understood to be the photochemical transformations of quinones, which form as intermediates in chlorophenol oxidation [8,23,24]. Therefore, an adequate kinetic and mechanistic study of the chemical oxidation of chlorophenols must be done in the dark in order to separate the thermal and photolytic components of the process [9,11,12].…”

Evaluation of Oxidation Process by Ozonation and Glucose Oxidase Enzyme on the Degradation of Benzoquinone in Wheat Flour

“…Finally, the BQs molecule responds to H 2 O 2 through the double bond between C3-C4 in the benzene ring, changing into 2, 3epoxy-p-benzoquinone. Under conditions of oxidation, 2, 3epoxy-p-benzoquinone transformed into aldehydes, ketones, acids, and CO 2 [24,25]. On the other hand, the ANOVA analyses of the results Table 1 show that the reduction or degradation of MBQ and EBQ depends significantly on the concentration of the GOX enzyme and the time of mixing (Eq.…”