Oxidation Of Model Compounds Research Articles

Efficient oxidative depolymerization of lignite through selective cleavage of cross-linked structures for producing oxygen-containing chemicals

The non-fuel utilization of lignite is of great significance, and mild oxidative depolymerization is a promising approach for producing oxygen-containing chemicals. In this work, Xiaolongtan lignite (XLT) was used to investigate selective oxidation under mild conditions, with the aim of avoiding excessive oxidation and reducing alkali consumption. The results demonstrate that O2 oxidation can efficiently depolymerize XLT into humic acid (HA) in diluted KOH aqueous solution. Under the optimized conditions (XLT/KOH mass ratio = 3, 3 MPa O2, 80 °C, 3 h), the HA yield can reach as high as 65.8%, with only a minimal amount of CO2 (3.1%) generated. In addition, the structure-oxidative depolymerization relationship was further examined through FTIR characterization and the oxidation of model compounds. The cleavage of cross-linked bonds, including methylene and ether bridge bonds as well as hydroaromatic rings, is essential for the depolymerization of lignite by O2 oxidation. The high stability of aliphatic substituents resulted in their enrichment in the oxidized residue (OR). Under mild conditions, the aromatic ring and aromatic carboxylic acids are stable and favors the production of HA. By combining with the oxidation of model compounds, a better understanding of the oxidative depolymerization of XLT to oxygen-containing chemicals is achieved.

Permanganate Oxidation of Organic Contaminants and Model Compounds.

Permanganate oxidation is an attractive environmental remediation strategy due to its low cost, ease of use, and wide range in reactivity. Here, permanganate reactivity trends are investigated for model organic compounds and organic contaminants. Second-order permanganate reaction rate constants were compiled for 215 compounds from 82 references (journal articles, conference proceedings, master's theses, and dissertations). Additionally, we validated some phenol rate constants and contribute a few additional phenol rate constants. Commonalities between contaminant oxidation products are also discussed, and we tentatively identify several model compound oxidation products. Aromatic rings, alcohols, and ether groups had low reaction rate constants with permanganate. Alkene reaction sites had the highest reaction rate constants, followed by phenols, anilines, and benzylic carbon-hydrogen bonds. Generally, permanganate reactivity follows electrophilic substitution trends at the reaction site where electron donating groups increase the rate of reaction, while electron withdrawing groups decrease the rate of reaction. Solution conditions, specifically, buffer type and concentration, may impact the rate of reaction, which could be due to either an ionic strength effect or the buffer ions acting as ligands. The impact of these solution conditions, unfortunately, precludes the development of a quantitative structure-activity relationship for permanganate reaction rate constants with the currently available data. We note that critical experimental details are often missing in the literature, which posed a challenge when comparing rate constants between studies. Future research directions on permanganate oxidation should seek to improve our understanding of buffer effects and to identify oxidation products for model compounds so that extrapolations can be made to more complex contaminant structures.

Electrochemical Oxidation and Bond Cleavage of Lignin-Derived Model Compounds with Nanoparticle Catalysts

Electrochemistry offer an environmentally friendly approach to convert biomass or biomass derived material into valuable organic chemicals, petrochemical substitutes, and energy-intensive chemicals. Monomers could be generated by cleaving ether (C-O-C) linkages in lignin via thermal decomposition process such as reductive catalytic fraction (RCF). However, this process leaves behind a significant portion of soluble lignin oligomers with recalcitrant C-C linkages. Monomer yields from the RCF pathway are approaching theoretical limits based on ether bond cleavage. Therefore, with broader goal of improving lignin utilization within a biorefinery, we probed the electrocatalytic oxidation of model dimer compounds with C-C linkages representative of RCF oligomers. Electrochemical studies offer several advantages including operation at low temperatures and pressures, applied potentials can be used to control reaction rates and selectivities, and renewable electricity can be used, thus lowering overall greenhouse gas emissions. According to previous studies, several metals such as nickel, cobalt, copper, and platinum can be used to build electrocatalysts for biomass conversion. Therefore, we have synthesized a series of low-cost nickel and molybdenum nanoparticle catalysts for the electrocatalytic oxidation of model compounds. Besides the high surface and high stability advantages of supported nanoparticles in general, these candidates exhibit interesting catalytic activities resembling that of noble metal catalysts such as platinum in oxygen reduction reaction (ORR) which could also be beneficial in bond cleavage reactions in biomass or biomass derived material. The focus of this talk will be on the electrochemical studies of the selected nanoparticle catalysts toward C-C bond cleavage in RCF dimer model compounds. The results from the studies also lead to some insights we may be able to use to guide the future development of electro-oxidation of RCF oil/ biomass stream. Besides metallic, phosphide and carbide nanoparticles on carbon support, metal foils were also tested and were used as a comparison. Notably, a MoC catalyst on carbon support showed C-C and C-O bond cleavage activities in aqueous alcoholic solution with sodium hydroxide as the electrolyte.

Chlorite formation during ClO2 oxidation of model compounds having various functional groups and humic substances

Chlorine dioxide (ClO2) has been used as an alternative to chlorine in water purification to reduce the formation of halogenated by-products and give superior inactivation of microorganisms. However, the formation of chlorite (ClO2−) is a major consideration in the application of ClO2. In order to improve understanding in ClO2− formation kinetics and mechanisms, this study investigated the reactions of ClO2 with 30 model compounds, 10 humic substances and 2 surface waters. ClO2− yields were found to be dependent on the distribution of functional groups. ClO2 oxidation of amines, di- and tri-hydroxybenzenes at pH 7.0 had ClO2− yields >50%, while oxidation of olefins, thiols and benzoquinones had ClO2− yields <50%. ClO2− yields from humic substances depended on the ClO2 dose, pH and varied with different reaction intervals, which mirrored the behavior of the model compounds. Phenolic moieties served as dominant fast-reacting precursors (during the first 5 min of disinfection). Aromatic precursors (e.g., non-phenolic lignins or benzoquinones) contributed to ClO2− formation over longer reaction time (up to 24 h). The total antioxidant capacity (indication of the amount of electron-donating moieties) determined by the Folin-Ciocalteu method was a good indicator of ClO2-reactive precursors in waters, which correlated with the ClO2 demand of waters. Waters bearing high total antioxidant capacity tended to generate more ClO2− at equivalent ClO2 exposure, but the prediction in natural water should be conservative.

A New Class of MnCeOx Materials for the Catalytic Gas Exhausts Emission Control: A Study of the CO Model Compound Oxidation

The effects of cerium addition on the physical–chemical properties and CO oxidation activity of nanocomposite MnCeOx catalysts (0 ≤ χCe ≤ 1) have been assessed. The kinetics of the CO oxidation on a typical nanocomposite MnCeOx catalyst (M5C1) were probed by temperature programmed catalytic reaction tests in the range of 293–533K. A systematic study of the interaction pattern of the catalyst with reagent and product molecules shows easy reactivity of surface oxygen to CO, low mobility of lattice oxygen and weak surface affinity to CO2. Systematic evidences on mechanism and intermediates signal an extrafacial redox path, triggered by the abstraction of oxygen atoms in the neighbouring of surface-active MnIV sites, and sustained by O2 species adsorbed on the resulting O-vacancies. A Langmuir–Hinshelwood (L–H) type reaction mechanism leads to a formal kinetic model fully predicting the CO oxidation functionality of the MnCeOx catalysts.

Three-dimensional composite of Co3O4 nanoparticles and nitrogen-doped reduced graphene oxide for lignin model compound oxidation

3D composite of Co3O4 nanoparticles and N-doped reduced graphene oxide can effectively catalyze the oxidation of lignin model compounds.

Studies on the Low-Temp Oxidation of Coal Containing Organic Sulfur and the Corresponding Model Compounds.

This paper selects two typical compounds containing organic sulfur as model compounds. Then, by analyzing the chromatograms of gaseous low-temp oxidation products and GC/MS of the extractable matter of the oxidation residue, we summarizing the mechanism of low-temp sulfur model compound oxidation. The results show that between 30 °C to 80 °C, the interaction between diphenyl sulfide and oxygen is mainly one of physical adsorption. After 80 °C, chemical adsorption and chemical reactions begin. The main reaction mechanism in the low-temp oxidation of the model compound diphenyl sulfide is diphenyl sulfide generates diphenyl sulfoxide, and then this sulfoxide is further oxidized to diphenyl sulphone. A small amount of free radicals is generated in the process. The model compound cysteine behaves differently from diphenyl sulfide. The main reaction low-temp oxidation mechanism involves the thiol being oxidized into a disulphide and finally evolving to sulfonic acid, along with SO2 being released at 130 °C and also a small amount of free radicals. We also conducted an experiment on coal from Xingcheng using X-ray photoelectron spectroscopy (XPS). The results show that the major forms of organic sulfur in the original coal sample are thiophene and sulfone. Therefore, it can be inferred that there is none or little mercaptan and thiophenol in the original coal. After low-temp oxidation, the form of organic sulfur changes. The sulfide sulfur is oxidized to the sulfoxide, and then the sulfoxide is further oxidized to a sulfone, and these steps can be easily carried out under experimental conditions. What’s more, the results illustrate that oxidation promotes sulfur element enrichment on the surface of coal.

Nitroxides protect against peroxynitrite-induced nitration and oxidation

Nitroxides are promising compounds for prevention of undesired protein modifications. The aim of this study was to compare the efficiency of 11 nitroxides, derivatives of 2,2,6,6-tetramethylpiperidine-1-oxide (TEMPO) and 2,2,5,5-tetramethylpirrolidine-1-oxyl (PROXYL) in prevention of nitration and oxidation of model compounds and human serum albumin (HSA). Most nitroxides were very efficient in preventing loss of fluorescein fluorescence induced by peroxynitrite (PN) (IC50 in the nanomolar range) and preventing HSA nitration. The loss of fluorescein fluorescence was demonstrated to be due to nitration. Nitroxides were more effective in prevention nitration than oxidation reactions. They showed a concentration window for preventing dihydrorhodamine (DHR) 123 oxidation but exerted a prooxidant effect at both high and low concentrations. No prooxidant effect of nitroxides was seen in prevention of DHR123 oxidation induced by SIN-1. In all essays hydrophobic nitroxides (especially 4-nonylamido-TEMPO and 3-carbamolyl-dehydroPROXYL) showed the lowest efficiency. An exception was the prevention of thiol group oxidation by PN and SIN-1 where hydrophobic nitroxides were the most effective, apparently due to binding to the protein. Nitroxides showed low toxicity to MCF-7 cells. Most nitroxides, except for the most hydrophobic ones, protected cells from the cytotoxic action of SIN-1 and SIN-1-induced protein nitration. These results point to potential usefulness of nitroxides for prevention of PN-induced oxidation and, especially, nitration.

PP48 - Prevention of peroxynitrite-induced nitration and oxidation by nitroxides

Peroxynitrite, formed in vivo in a reaction between nitric oxide and superoxide radical anion, is a compound of profound pathophysiological importance. The formation of peroxynitrite is intensified in many diseases, including neurodegenerative ones, and its reactions appear to contribute to the development of these diseases. Therefore, prevention of reactions of peroxynitrite may be useful in disease prevention and treatment. The aim of this study was to study the ability of nitroxides of various structures to prevent reactions of nitration and oxidation of model compounds and bovine serum albumin. Eleven nitroxides were used: 2,2,6,6-tetramethylpiperidine (TEMPO), 4-hydroxy-TEMPO, 4-amino-TEMPO, 4-oxo-TEMPO, 4-carboxy-TEMPO, 4-cyano-TEMPO, 4-methoxy-TEMPO, 4-acetamido-TEMPO, 4-nonylamido-TEMPO, 3-carbamoyl-PROXYL and 3-carbamoyl-dehydroPROXYL. Nitroxides were most effective in preventing peroxynitrite-induced decay of fluorescein (2 µM), conditioned by fluorescein nitration (IC50 of 40.0 ± 0.4 nM, 59.8 ± 0.6 nM and 64.4 ± 1,2 nM for the most effective nitroxides, viz. 4-hydroxy-TEMPO, 4-acetamido-TEMPO and 4-amino-TEMPO, respectively, and 3.72 ± 0.05 µM for the least effective 4-nonylamido-TEMPO). Nitroxides had a biphasic effect on the oxidation of dihydrorhodamine 123 (1 µM) by peroxynitrite, both low and high concentrations having a prooxidant effect. A protection window was observed for micromolar concentrations of nitroxides (maximal protective effect at 17.3 ± 2.3, 40 and 50.3 ± 20.7 µM for TEMPO, 4-hydroxy-TEMPO and 4-amino-TEMPO, respectively and > 400 for Pirolin and 4-nonylamido-TEMPO, the extent of maximal protection being 38-90%. Nitroxides (5 nM – 500 µM) were totally ineffective in preventing peroxynitrite-induced thiol oxidation of bovine serum albumin. These results demonstrate that nitroxides are more effective in preventing nitration than oxidation reactions.

Hydrocarbon Addition Reactions during Low-Temperature Autoxidation of Oilsands Bitumen

Low-temperature oxidation of bitumen with air in the temperature range of 130–160 °C was investigated. Of particular interest were the addition reactions taking place during oxidation, which contributed to the observed increase in viscosity of oxidized bitumen. During the autoxidation of bitumen, the relative aliphatic to aromatic loss-ratio of hydrogen increased from 18:1 to 30:1 when the temperature was increased from 140 °C to 150 °C and then remained almost the same at 160 °C. It coincided with a bitumen oxidation selectivity change reported in the literature. The hydrocarbon class responsible for most addition reactions during bitumen oxidation is the naphthenic-aromatic class. A model compound oxidation study at 130 °C found no addition products during paraffin oxidation, low addition product selectivity for naphthenic and alkylaromatic compounds, and no measurable oxidation of aromatics without alkyl groups. It was proposed that the dominant pathway for addition reactions of hydrocarbons is hydrogen disproportionation of free radicals to produce olefins. Free-radical addition to olefins through the formation of C–C bonds explained all of the oxidation selectivity observations from the model compound studies, as well as the addition products identified from their mass spectra. It could also be applied to explain the bitumen oxidation results in these and other studies.

Simultaneous production of small-molecule fatty acids and benzene polycarboxylic acids from lignite by alkali-oxygen oxidation

Alkali-oxygen oxidation of coals to produce high-value benzene polycarboxylic acids (BPCAs) is a potential route in the future. Among the coal ranks, lignite has been proved to be easily oxidized due to its low coalification, but the yield of BPCAs obtained from lignite is relatively low because of the low content of aromatic clusters in its structures. However, the aliphatic structures of lignite are relatively rich, which may be served as the mother structures for small-molecule fatty acids (SMFAs). Thus, in the present work, three lignites were oxidized in aqueous alkaline solutions by oxygen. SMFAs were detected and quantified in addition to BPCAs after the reaction. The results show that when the optimal BPCAs yields (18.4–21.5%) are obtained, large amount of SMFAs (39.8–23.2 wt.%) can be obtained simultaneously, including oxalic acid, formic acid, acetic acid, succinic acid and malonic acid. The oxidation of model compounds shows that SMFAs are mainly derived from the oxidation of aliphatic structures as well as the opening of benzene rings in the lignite structure.

Deep desulphurization of gas oil and model compounds by anatase nanocomposite sandwich type polyoxometalate as a novel, reusable and green nano mercaptan scavenger

Oxidative desulphurization of gas oil and model compounds that exist in gas oil with hydrogen peroxide/acetic acid using nanoparticle (Bu4N)7H3[P2W18Cd4(Br)2O68]-TiO2 ((Bu4N)7H3[P2W18Cd4]-TiO2) as a nano scavenger has been studied. This sandwich-type nanoparticle was shown be able to scavenge hydrogen sulfide and mercaptans with high yield. The addition of acetic acid enhanced the conversion. This system provides an efficient, convenient and practical method for scavenging of sulphur compound. The (Bu4N)7H3[P2W18Cd4]-TiO2 nanoparticle was very active catalyst system for the model compound oxidation, while other polyoxometalate systems were much less active.

Production of Benzene Polycarboxylic Acids from Lignite by Alkali-Oxygen Oxidation

The oxidation of coal to produce high-valued benzene polycarboxylic acids (BPCAs), which are obtained currently from diminishing petroleum reserves, is a promising industrial process of the future. Up to now, the yield distribution of BPCAs has not been studied in detail and the mechanism of coal oxidation to BPCAs remains unclear. In this study, Huolinhe lignite was oxidized in a batch reactor by alkali-oxygen oxidation. All 12 kinds of BPCAs obtained were quantified by a new established method. Effects of alkali/coal mass ratio, reaction temperature, initial oxygen pressure, and reaction time on the yield distribution of BPCAs were studied for the first time. The results indicate that BPCAs with four or five carboxyls are the predominant products, and BPCAs with one or two carboxyls are formed in a relatively short time; moreover, the formation of BPCAs with more carboxyls is relatively more sensitive to the salting out effect. CP/MAS 13C NMR spectra and oxidation of model compounds show that phenolic, ...

Peroxidase oxidation of lignin and its model compounds

The published information on the use of enzymes belonging to a large family of peroxidases of plant and fungal origin as the catalysts of lignin and its model compound oxidation by hydrogen peroxide are reviewed. The structures and the mechanism of the catalytic action of these enzymes are comparatively considered. The enzymes have similar structures; however, the enzymes of plant origin have higher stabilities and pH optima. It was concluded that further studies of the effect of the functional nature, polymolecular properties, and regularities of the redox conversions during the catalytic oxidation of plant lignins by plant peroxidases are promising.

Kinetics of the catalytic oxidation of model compounds of lignin with hydrogen peroxide in the presence of peroxidase from horse-radish

A kinetic scheme was suggested for the oxidation of guaiacol, ferulic acid, acetovanilon, and vanillyl alcohol with hydrogen peroxide. A number of kinetic parameters were determined.

Experiment study of model compound oxidation on spontaneous combustion of coal

Spontaneous combustion is one of the severest accidents in the process of coal production and transportation. Therefore it is significant to study the mechanism of coal spontaneous combustion. Based on theoretical analysis, 7 kinds of model compounds have been chosen in this paper, which are hyacinthin, anisole, diphenylmethane, phenetole, benzyl alcohol, benzhydrol, and aphenylpropanol. And they contain respectively active groups such as aldehyde group, methoxyl group, hypomethyl bond, hypomethylether bond, hypomethyl bond of a-carbon atom with hydroxyl, hypoalkyl bond of a-carbon atom with hydroxyl, and so on. According to the theory of free radical reactions, taking the model compound of coal above as research object, chemical reaction kinetic parameters, thermodynamic parameters, and products from normal temperature to 150°C have been quantitatively studied by oxidation device and analytical instrument, then the oxidation course can be deduced. The results show that all the model compounds consumed oxygen and produced CO and CO2 at different degrees after temperature programmed to 150°C. The oxidation characteristic of the active groups in coal and the effect of them on spontaneous combustion can be recognized, and spontaneous combustion mechanism can be exposited systematically in chemistry by means of studying the oxidation of model compound.

Electrochemical oxidation of model compounds and olive mill wastewater over DSA electrodes: 1. The case of Ti/IrO 2 anode

The electrochemical oxidation of olive mill wastewater (OMW) and model compounds over a Ti/IrO 2 anode was studied by means of cyclic voltammetry and bulk electrolysis. Experiments were conducted at 1300 mg/L initial COD, 0–1.23 V vs SHE and 1.4–1.54 V vs SHE potential windows, 50 mA/cm 2 current density, 0–25 mM NaCl, 60–80 °C temperature and acidic conditions. The reactivity of model compounds decreases in the order phenol ≈ p-coumaric acid > cinnamic acid > caffeic acid. Partial and total oxidation reactions occur with the overall rate following zero-order kinetics with respect to COD and increasing with temperature. Oxidation of OMW at 43 Ah/L, 80 °C and in the presence of 5 mM NaCl leads to complete color and phenols removal, elimination of ecotoxicity but moderate (30%) COD reduction. Similar performance can be achieved at 6 Ah/L in the presence of 15 mM NaCl. In the absence of salt, the respective color and phenols removal (at 6 Ah/L) is less than 10%. Excessive salinity (25 mM), although does not change color, phenols and COD removal, has an adverse effect on ecotoxicity.

DFT Calculation on the Stereochemistry of the Allylic Oxidation. Selenium Dioxide-Mediated Oxidation of an Exocyclic Olefinic Hydrindane Compound

Selenium dioxide-mediated oxidation is among the most important transformations for introducing an hydroxy group into the allylic position in the substituted alkenes in organic and biochemical pathways. A unique mode of highly stereoselective interaction of selenium dioxide with olefins, resulting in allylic alcohols, is well exemplified for the preparation of a steroid compound as shown Scheme 1. Since Sharpless and Lauer proposed a mechanism, generally accepted, for this process in 1972 as resulting from an initial ene reaction followed by a [2,3]-sigmatropic rearrangement, there have been considerable efforts on particularly clarifying the stereo-selectivity of this reaction. For example, Singleton and Hang clarified a concerted aspect of the ene step in the allylic oxidation of 2-methyl-2-butene with selenium dioxide (1 → 2 in Scheme 2). Recently we have elucidated the overall pathways in detail by treating theoretically both an ‘ene’ reaction and the 2,3-sigmatropic rearrangement involved in this selenium dioxide-mediated oxidation of 1: the allylic oxidation occurs by complex mechanisms via two competing paths such as anti-approach and syn-approach in the ‘ene’ reaction to produce the (E)allylic alcohol 2, where it has been first noticed the Cα-Cβ bond rotation in 2,3-rearrangement step plays an important part for the stereo-selectivity of the reaction. Now our attention is brought to understand the consequence of the Cα-Cβ bond rotation in the selenic acid intermediate produced from the ene step as to whether it may affects the stereochemical course of the allylic oxidation of a hydrindane compound 5, where an exocyclic olefinic structure is crafted (Scheme 3). Here, we report the results of ab initio studies of the allylic oxidation of 5, focusing on analyzing whether the conformational change via bond rotation in selenic acid intermediate 6 may give rise to produce 9. To study the reaction pathway with relative stabilities for possible transition states during the allylic oxidation of model compound 5 (Scheme 4 and Table 1), we have investigated the energy of possible transition states in SeO2 oxidation of 5 by b3lyp/6-31G* calculation. In ene reaction step, the anti approach of selenium dioxide is energetically favored than the syn one by 1.82 kcal/mol (entry 2 and 3 in Table 1). In the following 1,3-rearrangement step, the O=Segroup approach to the α face of double bond is more favorable than the β face by 2.28 kcal/mol (entry 4 and 5 in Table 1). The compound 7 as a major product should be obtained by the pathway of ts-1a and ts-1a-2α. The other isomer 9 can be formed through the pathway of ts-1a and ts1a-2β, where a Cα-Cβ bond rotation of the ‘ene’ reaction

Oxidative Desulfurization of Diesel Oil Using Mesoporous Phosphotungstic Acid/SiO2 as Catalyst

AbstractOrdered mesoporous phosphotungstic acid/SiO2 (HPW/SiO2) with Keggin‐type heteropolyacids (HPAs) encapsulated into a SiO2 framework has been synthesized and used as the catalyst for oxidative desulfurization of diesel fuel. The sulfur compounds in diesel were oxidized and removed at a temperature range of 50–80 °C with H2O2 as the oxidant and acetonitrile as the extraction agent. The sulfur content in diesel was reduced to as low as 48–86 μg/g from the initial level of 438 μg/g. The loss in catalytic activity was negligible even after five cycles of use, and the reduction of the sulfur content was enhanced with increasing the immobilized phosphotungstic acid (HPW) concentration. Oxidation of model compounds showed that in the heterogeneous system both the electron density and the steric hindrance affected the reactivity of these sulfur compounds. The reactivities of these sulfur compounds studied in this work followed the order of dibenzothiophene &gt; 4,6‐dimethydibenzothiophene &gt; benzothiophene.

Oxidation of Thiophenes over Silica Gel in Hydrogen Peroxide/Formic Acid System

Thiophene (C 4H 4S) and 3-methylthiophene(3-MC 4S) are typical thiophenenic sulfur compounds that exist in fluid catalytic cracking (FCC) gasoline. Oxidation of C 4H 4S and 3-MC 4H 4S were conducted in hydrogen peroxide (H 2O 2) and formic acid system over a series of silica gel loaded with metal oxide. The silica gel loaded with copper and cobalt (1:1) oxide was found very active for the model compound oxidation using H 2O 2/formic acid, while the silica gel unloaded with metal oxide was less active. The sulfur removal rate of thiophenes was different as solvent was changed. And the conversation of C 4H 4S and 3-MC 4H 4S was improved at higher temperature, but reduced when olefin was added. The sulfur removal rate of model sulfur compounds was enhanced when the phase transfer catalyst emulsifier polyethylene glycol octyl phenyl ether or tetrabutylammonium bromide(TBAB) was added. The sulfur removal rate of simulated gasoline containing 524μg·ml −1 sulfur reached 90%. Interestingly, in a H 2O 2 and formic acid system with the addition of TBAB, a bromine substitution trend appeared in the oxidation of thiophenes, suggesting the influence of TBAB.