Theoretical Study of the Oxidation Mechanism of Hematoxylin in Aqueous Solution

2012 ◽  
Vol 65 (5) ◽  
pp. 486 ◽  
Author(s):  
Mansoor Namazian ◽  
Hamid R. Zare ◽  
Michelle L. Coote
Keyword(s):  
Aqueous Solution ◽  
Experimental Study ◽  
Electrochemical Oxidation ◽  
Chemical Reaction ◽  
Oxidation Mechanism ◽  
Oxidation Potential ◽  
Hydroxyl Groups ◽  
Standard Hydrogen Electrode ◽  
Hydrogen Electrode ◽  
Irreversible Chemical Reaction

The oxidation of the two catechol rings A and B in the chemical structure of hematoxylin in aqueous solution has been studied theoretically in order to identify the mechanism of oxidation. In a recent experimental study, the oxidation mechanism of hematoxylin was designated an ErCiEr process in which an irreversible chemical reaction (Ci) followed the reversible chemical electrochemical oxidation (Er) of the catechol unit connected to the six-membered ring of the molecule (ring A). The theoretical results presented herein indicate that the electrochemical oxidation of ring B is actually slightly more favoured than ring A, although the potential separation is so small that they were unable to be distinguished in the experimental study. We therefore suggest that the most likely mechanism is ErErCiEr, in which two reversible electrochemical oxidation reactions (Er) occur preceding the irreversible chemical reaction (Ci), though we cannot rule out a contribution from ErCiEr. The calculated oxidation potential (0.719 V v. standard hydrogen electrode) is in close accord with the experimental value (0.759 V v. standard hydrogen electrode). The deprotonation of five hydroxyl groups of hematoxylin in aqueous solution is also studied and the order of acidic strength of these groups has been identified.

Photooxidation at Platinum Colloidal TiO2 Aqueous-Solution Interfaces. I. Ethylenediaminetetraacetic Acid and Related-Compounds

1986 ◽  
Vol 39 (5) ◽  
pp. 757 ◽  
Author(s):  
DN Furlong ◽  
D Wells ◽  
WHF Sasse
Keyword(s):  
Carbon Dioxide ◽  
Aqueous Solution ◽  
Ethylenediaminetetraacetic Acid ◽  
Oxidation Potential ◽  
Illumination Time ◽  
Carbonium Ions ◽  
Production Of Hydrogen ◽  
Glycine Derivatives ◽  
Lactic Acids ◽  
Exhaustive Oxidation

The photooxidation of ethylenediaminetetraacetic acid ( edta ) and related glycine derivatives, at Pt/TiO2/aqueous solution interfaces, has been monitored via the production of hydrogen and carbon dioxide. Yields are consistent with the exhaustive oxidation of methoxycarbonyl groups and the rate varied with the number and distribution of such groups. A photooxidation pathway is proposed which involves the oxidation of intermediate carbonium ions. Plausible molecular intermediates, such as formic acid and formaldehyde in the case of edta , have been shown in separate experiments to be photooxidized according to the proposed pathway. The maximum rate of oxidation for each donor depends on its oxidation potential and its tendency to adsorb on TiO2 surfaces. Desorption due to pH increase, as well as consumption of the donor, causes the rate to decline rapidly with illumination time. Acetic and malonic acids gave some hydrogen but underwent mainly (> c. 80%) photo-Kolbe decarboxylation to yield carbon dioxide and methane. By contrast the oxidation of oxomalonic, pyruvic and lactic acids proceeded mainly via a H2 producing pathway similar to that established for edta. The oxidation of pyruvic and lactic acids ceased at a yield of one mole of CO2 per mole of acid.

Multi-Pathway Excited State Relaxation of Adenine Oligomers in Aqueous Solution: A Joint Theoretical and Experimental Study

2013 ◽  
Vol 19 (11) ◽  
pp. 3762-3774 ◽  
Author(s):  
Akos Banyasz ◽  
Thomas Gustavsson ◽  
Delphine Onidas ◽  
Pascale Changenet-Barret ◽  
Dimitra Markovitsi ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Experimental Study ◽  
Excited State

Enhanced Electrochemical Oxidation of BH4− on Pt Electrode in Alkaline Electrolyte with the Addition of Thiourea

2010 ◽  
Vol 132 ◽  
pp. 271-278 ◽  
Author(s):  
Dan Mei Yu ◽  
Chang Guo Chen ◽  
Shu Lei ◽  
Xiao Yuan Zhou ◽  
Guo Zhong Cao
Keyword(s):  
Cyclic Voltammetry ◽  
Electrochemical Oxidation ◽  
Electrochemical Impedance ◽  
Alkaline Electrolyte ◽  
Hydroxyl Groups ◽  
Catalytic Hydrolysis ◽  
Direct Oxidation ◽  
Pt Electrode ◽  
Separation Membrane ◽  
And Diffusion

The electrochemical oxidation of sodium borohydride (NaBH4) on Pt electrode in alkaline electrolyte with the addition of thiourea has been studied by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry (CP). NaBH4 is readily to react with hydroxyl groups to release hydrogen through either direct oxidation or catalytic hydrolysis. The experimental results demonstrated that the addition of an appropriate amount of thiourea to the alkaline electrolyte resulted in the suppression of catalytic hydrolysis and diffusion of borohydride ions through the separation membrane.

scholarly journals Electrochemical oxidation of sulfamethoxazole using Ti/SnO2-Sb/Co-PbO2 electrode through ANN-PSO

2019 ◽  
Vol 84 (7) ◽  
pp. 713-727 ◽  
Author(s):  
Jiteng Wan ◽  
Chunji Jin ◽  
Banghai Liu ◽  
Zonglian She ◽  
Mengchun Gao ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Electrochemical Oxidation ◽  
Removal Efficiency ◽  
Current Density ◽  
Ph Value ◽  
Ann Model ◽  
Solution Ph ◽  
Pbo2 Electrode ◽  
Artificial Neural Network Ann ◽  
Major Factors

Even in a trace amounts, the presence of antibiotics in aqueous solution is getting more and more attention. Accordingly, appropriate technologies are needed to efficiently remove these compounds from aqueous environments. In this study, we have examined the electrochemical oxidation (EO) of sulfamethoxazole (SMX) on a Co modified PbO2 electrode. The process of EO of SMX in aqueous solution followed the pseudo-first-order kinetics, and the removal efficiency of SMX reached the maximum value of 95.1 % within 60 min. The effects of major factors on SMX oxidation kinetics were studied in detail by single-factor experiments, namely current density (1?20 mA cm-2), solution pH value (2?10), initial concentration of SMX (10?500 mg L-1) and concentration of electrolytes (0.05?0.4 mol L-1). An artificial neural network (ANN) model was used to simulate this EO process. Based on the obtained model, particle swarm optimization (PSO) was used to optimize the operating parameters. The maximum removal efficiency of SMX was obtained at the optimized conditions (e.g., current density of 12.37 mA cm-2, initial pH value of 4.78, initial SMX concentration of 74.45 mg L-1, electrolyte concentration of 0.24 mol L-1 and electrolysis time of 51.49 min). The validation results indicated that this method can ideally be used to optimize the related parameters and predict the anticipated results with acceptable accuracy.

scholarly journals The Role of Carboxyl and Hydroxyl Groups of Humic Acid in Removing AuCl4- from Aqueous Solution

2017 ◽  
Vol 17 (1) ◽  
pp. 95 ◽  
Author(s):  
Sri Sudiono ◽  
Mustika Yuniarti ◽  
Dwi Siswanta ◽  
Eko Sri Kunarti ◽  
Triyono Triyono ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Humic Acid ◽  
Peat Soil ◽  
Sharp Decrease ◽  
Hydroxyl Groups ◽  
Mixed Solution ◽  
Oh Groups ◽  
Characterization Result ◽  
Ft Ir

Humic acid (HA) extracted from peat soil according to the recommended procedure of the International Humic Substances Society (IHSS) has been tested to remove AuCl4- from aqueous solution. The removal was optimum at pH 2.0 and it was mainly dictated by attachment through hydrogen bonding to unionized carboxyl (–COOH) groups and reduction by the action of the hydroxyl (–OH) groups to gold (Au) metal. The removal of AuCl4- improved after HA was purified through repeated immersion and shaking in a mixed solution containing 0.1 M HCl and 0.3 M HF. When the purification led to the sharp decrease in ash content from 39.34 to 0.85% (w/w) and significant increase in both the –COOH and –OH contents from 3240 to 3487 mmol/kg and from 4260 to 4620 mmol/kg, respectively; the removal of AuCl4- improved from 0.105 to 0.133 mmol/g. This improvement of AuCl4- removal by the purified HA was accompanied by higher ability in reduction to Au metal. The attached AuCl4- on –COOH groups of both crude and purified HAs was qualitatively observed by the characterization result of FT-IR spectroscopy, while the presence of Au metal on the surface of those HAs was verified by the characterization result of XRD.

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