Oxidation and chemiluminescence of catechol by hydrogen peroxide in the presence of Co(II) ions and CTAB micelles

Abstract

The oxidation of catechol in neutral and slightly alkaline aqueous solutions (pH 7-9.6) by excess hydrogen peroxide (0.002-0.09 mol/L) in the presence of Co(II) (2.10(-7)-2.10(-5) mol/L) is accompanied by abrupt formation of red purple colouration, which is subsequently decolourized within 1 h. The electron spectra of the reaction mixture are characterized by a broad band covering the whole visible range (400-700 nm), with maximum at 485 nm. The reaction is initiated by catechol oxidation to its semiquinone radical and further to 1,2-benzoquinone. By nucleophilic addition of hydrogen peroxide into the p-position of benzoquinone C=O groups, hydroperoxide intermediates are formed, which decompose to hydroxylated 1,4-benzoquinones. It was confirmed by MS spectroscopy that monohydroxy-, dihydroxy- and tetrahydroxy-1,4-benzoquinone are formed as intermediate products. As final products of catechol decomposition, muconic acid, its hydroxy- and dihydroxy-derivatives and crotonic acid were identified. In the micellar environment of hexadecyltrimethylammonium bromide the decomposition rate of catechol is three times faster, due to micellar catalysis, and is accompanied by chemiluminescence (CL) emission, with maxima at 500 and 640 nm and a quantum yield of 1 x 10(-4). The CL of catechol can be further sensitized by a factor of 8 (maximum) with the aid of intramicellar energy transfer to fluorescein.

Hot Hole Hopping in a Polyoxotitanate Cluster Terminated with Catechol Electron Donors

“…5 The short wavelength band is dominated by the absorbance of the hole, i.e., the radical cation of the oxidized catechol ligand. 36,37 The formation of the chargeseparated state is complete within the ∼100 fs temporal resolution of our experiments. The decay of the broad spectrum is homogeneous, with only a hint of a dynamic blue shift at very early times, which is consistent with intramolecular vibrational relaxation (IVR).…”

Liquid Metal-Triggered Assembly of Phenolic Nanocoatings with Antioxidant and Antibacterial Properties

“…This is further corroborated by the appearance of characteristic brownish color (Figure S7) of the phenolic solutions, indicating the formation of ortho-quinones, which is consistent with the observations reported for the auto-oxidation of di- or trihydroxy phenolic groups at pH values around 7 or higher . Similarly, the resulting green-brownish coloration of PC with two absorbance peaks at 400 and 700 nm may correspond to the formation of catechol semiquinone as an intermediate oxidation product . The effect of polyphenol/AP ratio on the oxidation kinetics was also monitored for PG, where the kinetics were found to increase with increasing ratio of 1:0.5 to 1:5.0 (Figure S10).…”

“…36 Similarly, the resulting green-brownish coloration of PC with two absorbance peaks at 400 and 700 nm may correspond to the formation of catechol semiquinone as an intermediate oxidation product. 37 The effect of polyphenol/AP ratio on the oxidation kinetics was also monitored for PG, where the kinetics were found to increase with increasing ratio of 1:0.5 to 1:5.0 (Figure S10).…”

Fiber-Optic Plasmonic Sensor Utilizing CTAB-Functionalized ZnO Nanoparticle-Decorated Carbon Nanotubes on Silver Films for the Detection of Catechol in Wastewater

“…10 However, these methods require extremely specialized costly instruments and trained professionals for operation, which make the whole sensing process very expensive and cumbersome. Other experimental techniques like voltammetry, 7 spectrophotometry, 11 colorimetry, 6 chemiluminescence, 9 and capillary electrophoresis 12 are also extensively reviewed in the literature for the sensing of catechol. However, the low sensitivity, false alarms, and the need for a complex sample pretreatment make these techniques difficult for commercial use.…”

“…It is considered to be a human group 2B carcinogen by the International Agency for Research on Cancer (IARC). The lethal human dose for catechol is 50–500 mg/kg. − Because of these reasons, it is classified as a serious organic environmental pollutant at a concentration as low as 1 ppm (9 μM) by the U.S. Environmental Protection Agency and European Union. Hence, simple, fast, field-portable, and accurate analytical methods are required for the quantitative determination of catechol due to the associated environmental, food-related, and the biological concerns.…”