Reaction Of Catechol Research Articles

Zirconium-catalyzed one-pot synthesis of benzoxazoles using reaction of catechols, aldehydes and ammonium acetate

In this study, an efficient method for the synthesis of benzoxazoles by coupling catechols, aldehydes and ammonium acetate using ZrCl4 as catalyst in ethanol is reported. A wide range of benzoxazoles (59 examples) are smoothly produced in high yields (up to 97%). Other advantages of the method include large-scale synthesis and the use of oxygen as an oxidant. The mild reaction conditions allowed late-stage functionalization, facilitating access to several derivatives with biologically relevant structures such as β-lactam and quinoline heterocycles.

Research on surface modification of polypropylene fiber and its application evaluation in oil well cement

In order to improve the compatibility and dispersibility of polypropylene fiber (PPF) in oil well cement and enhance the mechanical properties of cementing cement sheath, the surface modification of PPF was carried out in this study. After surface impurity removal of PPF, reaction of catechol with polyamines, and subsequent treatment with γ- aminopropyltriethoxysilane (KH-550) and Ethyl orthosilicate (TEOS), modified polypropylene fiber (MPF) was obtained. The MPF was characterized and analyzed using FTIR, XPS, SEM, and EDS, showing a transformation in the surface properties of the fibers. The most significant change was that the contact angle between MPF and water decreased from 123.87 ° to 46.32 °, marking the successful transition of the fiber from hydrophobicity to hydrophilicity. Image analysis showed that the dispersion of MPF improved significantly. The dispersion coefficient of MPF in water and cement stone was increased by 86.90% and 14.48% compared with PPF, respectively. The effect of MPF on mechanical properties of oil well cement stone was studied. The comparative analysis results showed that MPF can significantly improve the flexural and compressive strength of the cement matrix. The flexural and compressive strength of cement stone mixed with MPF were increased by 10.25% and 6.43%, respectively, compared to cement stone mixed with PPF. SEM, MIP, and fiber single fiber pull-out experiments showed that the porosity of cement stone added with MPF was lower, the rough surface structure of MPF enhanced the bonding between fibers and cement stone, and the bridging effect of fibers in cement stone ultimately improved the mechanical properties of oil well cement stone.

MnO@C composites derived from MOFs coated with reduced graphene oxide for simultaneous detection of catechol and hydroquinone

AbstractIn this work, manganese‐based metal‐organic frameworks (MnBDC) were synthesized by solvothermal method and physically mixed with pre‐prepared graphene oxide (GO) to obtain GO/MnBDC, which were calcined to give MnO@C composite coated with reduced graphene oxide (rGO) marked as rGO/MnO@C. The materials were characterized by SEM, XRD, FTIR and XPS. Based on this composite, a novel sensor was constructed on a glassy carbon substrate, which exhibited good electrocatalytic activities to the redox reactions of catechol (CC) and hydroquinone (HQ), enabling simultaneous detection of both analytes. Under optimized conditions, the electrochemical sensor demonstrated a linear range of 0.50–90.00 μM for both CC and HQ detection, with respective detection limits of 0.05 μM and 0.03 μM. Moreover, the sensor exhibited excellent sensitivity, selectivity and accuracy for detecting CC and HQ simultaneous in real samples.

Details of exit channel dynamics of the ozonolysis of catechol in condensed phase: Product channels and product energy partitioning

Direct dynamics simulations on the ozonolysis reaction of catechol is performed in a vacuum and in an N2 bath to study the various aspects of the exit channel dynamics of the reaction. The simulations were conducted at 20 and 324 kg/m3 densities, with 200 and 293 N2 molecules in the bath, respectively. It is a post-transition state (TS) direct dynamics simulation, where the TS of the catechol+O3 system is taken as the reactant. High combustion temperatures of 800, 1000, and 1500 K are considered for the reactant excitation. In contrast, the bath is taken at 300 K. CO, H2O, CO2, O2, and small carboxylic acid (SCA) are the major channels observed for this reaction. Explicit study of the product channels along with rate constants of all the product channels are obtained. The rate constants are in the order of ns−1. The partitioning of the product's internal energy into its various modes and how the energy transfer occurs in the formation of the products is an exciting aspect of the study. Also reported in this work is the branching ratio of the products and comparison with the experimentally reported data. The energy partitioning study reveals that the dissociation dynamics of the catechol-O3 TS is not statistical. In contrast, the bath dynamics, which correspond to the energy transfer from the TS to the bath, is statistical in nature.

Disposable Pencil Lead as an Electrochemical Transducer for Monitoring Catechol in River and Tap Water

A cheap and disposable pencil graphite electrode (PGE) was developed by the incorporation of amine groups (Am-PGE-1). A further improvement in the performance was observed when the aminated electrode (Am-PGE-1) was activated by applying a negative potential scan (Am-PGE-2). The electrochemical transport properties were evaluated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The Nyquist plot showed a reduced charge transfer resistance value of 24.3 Ω for Am-PGE-2, while it was 95.1 Ω for bare PGE. Thus, Am-PGE-2 was used as a sensing platform for the detection of catechol. It was found that the electrochemical response of catechol oxidation at Am-PGE-2 was twice than the current obtained for bare PGE. Additionally, the effect of pH of the supporting electrolyte and reaction kinetic were studied. The heterogeneous electron transfer rate constant was calculated to be 0.01 s−1. Moreover, CV study revealed that the redox reaction of catechol was a quasi-reversible and diffusion-controlled process. The square wave voltammetry (SWV) technique was applied for the quantitative determination of catechol. The peak current showed a linear dependency on the concentration of catechol from 3 to 150 µM. Furthermore, the analyte could be detected as low as 3.86 µM. Likewise, the sensor demonstrates a good selectivity towards the target analyte than the other possible interfering molecules or ions. Aiming to examine practical applicability, real samples, such as river and household tap water, were tested by using the proposed transducer, and the satisfactory recoveries demonstrate the effectiveness of Am-PGE-2 in real life applications.

Laccase-Carrying Polylactic Acid Electrospun Fibers, Advantages and Limitations in Bio-Oxidation of Amines and Alcohols.

Laccases are oxidative enzymes that could be good candidates for the functionalization of biopolymers with several applications as biosensors for the determination of bioactive amine and alcohols, for bioremediation of industrial wastewater, and for greener catalysts in oxidation reactions in organic synthesis, especially used for non-phenolic compounds in combination with redox mediators in the so-called Laccase Mediator System (LMS). In this work, we describe the immobilization of Laccase from Trametes versicolor (LTv) in poly-L-lactic acid (PLLA) nanofibers and its application in LMS oxidation reactions. The PLLA-LTv catalysts were successfully produced by electrospinning of a water-in-oil emulsion with an optimized method. Different enzyme loadings (1.6, 3.2, and 5.1% w/w) were explored, and the obtained mats were thoroughly characterized. The actual amount of the enzyme in the fibers and the eventual enzyme leaching in different solvents were evaluated. Finally, the PLLA-LTv mats were successfully applied as such in the oxidation reaction of catechol, and in the LMS method with TEMPO as mediator in the oxidation of amines with the advantage of easier work-up procedures by the immobilized enzyme. However, the PLLA-LTv failed the oxidation of alcohols with respect to the free enzyme. A tentative explanation was provided.

Quinoline Derivatives with Different Functional Groups: Evaluation of Their Catecholase Activity

In this work, we are interested in finding new catalysts for catecholase, whose principle is based on the oxidation reaction of catechol to o-quinone. In this context, we have studied a series of seven quinoline-based compounds. The present work indicates that the complexes formed between seven selected quinoline compounds and the copper salts viz. Cu(OAc)2, CuSO4, Cu(NO3)2, and CuCl2 elicit catalytic activities for the oxidation of catechol to o-quinone. The complexes formed with the Cu(OAc)2 salt show a much higher catalytic activity than the others, whereas the Cu(NO3)2 and CuCl2 salts formed complexes with low catalytic activity. This study also shows that the oxidation rate depends on two factors, namely the chemical structure of the ligands and the nature of the ions coordinated with the copper.

Insights into the Binding Interaction of Catechol 1,2-Dioxygenase with Catechol in Achromobacter xylosoxidans DN002.

Microbial remediation has become one of the promising ways to eliminate polycyclic aromatic hydrocarbons (PAHs) pollution due to its efficient enzyme metabolism system. Catechol 1,2-dioxygenase (C12O) is a crucial rate-limiting enzyme in the degradation pathway of PAHs in Achromobacter xylosoxidans DN002 that opens the benzene ring through the ortho-cleavage pathway. However, little attention has been given to explore the interaction mechanism of relevant enzyme-substrate. This study aims to investigate the binding interaction between C12O of strain DN002 and catechol by means of a molecular biological approach combined with homology modeling, molecular docking, and multiple spectroscopies. The removal rate of catechol in the mutant strain of cat A deletion was only 12.03%, compared to the wild-type strain (54.21%). A Ramachandran plot of active site regions of the primary amino acid sequences in the native enzyme showed that 93.5% sequences were in the most favored regions on account of the results of homology modeling, while an additional 6.2% amino acid sequences were found in conditionally allowed regions, and 0.4% in generously allowed regions. The binding pocket of C12O with catechol was analyzed to obtain that the catalytic trimeric group of Tyr164-His224-His226 was proven to be great vital for the ring-opening reaction of catechol by molecular docking. In the native enzyme, binding complexes were spontaneously formed by hydrophobic interactions. Binding constants and thermodynamic potentials from fluorescence spectra indicated that catechol effectively quenched the intrinsic fluorescence of C12O in the C12O/catechol complex via conventional static and dynamic quenching mechanisms of C12O. The results of ultraviolet and visible (UV) spectra, synchronous fluorescence, and circular dichroism (CD) spectra revealed conspicuous changes in the local conformation, and site-directed mutagenesis confirmed the role of predicted key residues during catalysis, wherein His226 had a significant effect on catechol utilization by C12O. This is the first report to reveal interactions of C12O with substrate from the molecular docking results, providing the mechanistic understanding of representative dioxygenases involved in aromatic compound degradation, and a solid foundation for further site modifications as well as strategies for the directed evolution of this enzyme.

Photo-oxidation and Photoreduction of Catechols by Chlorophyll Metabolites and Methylene Blue.

While plant-derived oxidants can protect cells from oxidative damage, limited research has examined the role of dietary chlorophyll. Photoreduction of ubiquinone by chlorophyll metabolites and red light has been reported in vitro and in animal models. Herein we examined photo-oxidation and photoreduction reactions of catechols, dopamine and hydrocaffeic acid. Photo-oxidation of dopamine by methylene blue and the chlorophyll metabolites pheophorbide A, chlorin e6 and sodium copper chlorophyllin was studied by monitoring aminochrome, the cyclized product of the dopamine o-quinone with its amine. Singlet oxygen scavengers including sodium azide, ascorbate and glutathione decreased aminochrome formation by methylene blue and pheophorbide A. Addition of EDTA, a tertiary amine electron donor, to the reaction of dopamine, photosensitizer and red light decreased aminochrome formation. Photoreduction of the dopamine o-quinone produced by mushroom tyrosinase was achieved by both methylene blue and pheophorbide A only when an electron donor was included. Due to limited solubility, photo-oxidation and photoreduction reactions by pheophorbide A required 5-7.5% dimethylformamide for optimal reactivity. Catalytic photoreduction of 2,3-dimethoxy-5-methyl-p-benzoquinone by methylene blue or pheophorbide A and tertiary amine electron donors was observed. Among the chlorophyll metabolites, pheophorbide A was more effective than chlorin e6 or sodium copper chlorophyllin in photo-oxidation of dopamine and photoreduction reactions. Singlet oxygen inhibited lactate dehydrogenase A activity, and higher molecular weight protein cross-links were observed on SDS-PAGE. Hydrocaffeic acid competed with lactate dehydrogenase A for reaction with singlet oxygen produced by methylene blue; however, no protection by hydrocaffeic acid (HCA) was observed when pheophorbide A was used. Cysteine modification of lactate dehydrogenase A by the o-quinone of hydrocaffeic acid was detected using a redox cycling stain. Inclusion of an electron donor decreased protein labeling.

Post-Transition-State Direct Dynamics Simulations on the Ozonolysis of Catechol.

On-the-fly dynamics simulations are performed for the reaction of catechol + O3. The post transition state (TS) dynamics is studied at temperatures of 400 and 500 K. The PM7 semiempirical method is employed for calculating the potential energy gradient needed for integrating Hamilton's equations of motion. This semiempirical method provides excellent agreement in terms of energy and geometry of the TSs as well as minimum energy states of the system with respect to B3LYP/6-311+G (2df, 2p) calculated results. In the dynamics, first, a peroxyacid is formed, which further dissociates to different fragments. Four major channels forming CO, CO2, H2O, and small carboxylic acid (SCA) fragments are seen in this reaction. Rates of each of the channels and the overall unimolecular reaction are calculated at both temperatures. Branching ratios of all these product channels are calculated and compared with experiment. The minimum energy profile of CO2, CO, and H2O channels are calculated. A qualitative estimate of activation energies for all the channels are obtained and compared with the explicit TS energies of three product channels, which ultimately correlate with the reaction probabilities.

Polyethylene Glycols Catalyzed Reaction of Catechol and Resorcinol with Cerium Ammonium Sulfate in the Aqueous Medium: Kinetic and Mechanistic Study

Polyethylene Glycols Catalyzed Reaction of Catechol and Resorcinol with Cerium Ammonium Sulfate in the Aqueous Medium: Kinetic and Mechanistic Study

Correction to “Loading of Antibiotics into Polyelectrolyte Multilayers after Self-Assembly and Tunable Release by Catechol Reaction”

Correction to “Loading of Antibiotics into Polyelectrolyte Multilayers after Self-Assembly and Tunable Release by Catechol Reaction”

Study of the Catecholase Activity of new catalysts Based on Copper (II) and Heterocyclic Ligands

In this work, we are interested in finding new catalysts for catecholase, whose principle is based on the oxidation reaction of catechol to o-quinone. We approached the synthesis of the threes tripod ligands based on pyrazole in a condensation reaction and its characterization by IR, 13C NMR, 1H NMR spectroscopy, then we evaluated the catalytic properties of certain complexes formed in situ to catalyze the oxidation reaction of catechols to o-quinones. The aim is to find the right models to reproduce the catalytic activity of the enzyme (catecholase), we used complexes formed in situ by pyrazole derivatives with Copper salts. Among these complexes, the complex L4/Cu(CH3COO)2 showed good catalytic activity of the combination (1ligand/2metal) in MeOH for this reaction, with a speed Vmax equal to 69.38 μmol.L-1.min-1 and a low value of Km equal to 0.019 mol.L-1. We have demonstrated that the nature of concentration, ligand, solvent, and copper salts, influenced strongly the catecholase activity.

Mechanistic understanding of catechols and integration into an electrochemically cross-linked mussel foot inspired adhesive hydrogel

Catechol reaction mechanisms form the basis of marine mussel adhesion, allowing for bond formation and cross-linking in wet saline environments. To mimic mussel foot adhesion and develop new bioadhesive underwater glues, it is essential to understand and learn to control their redox activity as well as their chemical reactivity. Here, we study the electrochemical characteristics of functionalized catechols to further understand their reaction mechanisms and find a stable and controllable molecule that we subsequently integrate into a polymer to form a highly adhesive hydrogel. Contradictory to previous hypotheses, 3,4-dihydroxy-L-phenylalanine is shown to follow a Schiff-base reaction whereas dopamine shows an intramolecular ring formation. Dihydrocaffeic acid proved to be stable and was substituted onto a poly(allylamine) backbone and electrochemically cross-linked to form an adhesive hydrogel that was tested using a surface forces apparatus. The hydrogel's compression and dehydration dependent adhesive strength have proven to be higher than in mussel foot proteins (mfp-3 and mfp-5). Controlling catechol reaction mechanisms and integrating them into stable electrochemically depositable macroscopic structures is an important step in designing new biological coatings and underwater and biomedical adhesives.

Tannic Acid as a Natural Crosslinker for Catalyst-Free Silicone Elastomers From Hydrogen Bonding to Covalent Bonding.

The construction of silicone elastomers crosslinked by a natural crosslinker under a catalyst-free method is highly desirable. Herein we present catalyst-free silicone elastomers (SEs) by simply introducing tannic acid (TA) as a natural crosslinker when using poly (aminopropylmethylsiloxane-co-dimethylsiloxane) (PAPMS) as the base polymer. The crosslinked bonding of these SEs can be easily changed from hydrogen bonding to covalent bonding by altering the curing reaction from room temperature to heating condition. The formability and mechanical properties of the SEs can be tuned by altering various factors, including processing technique, the amount of TA and aminopropyl-terminated polydimethylsiloxane, the molecular weight and -NH2 content of PAPMS, and the amount of reinforcing filler. The hydrogen bonding was proved by the reversible crosslinking of the elastomers, which can be gradually dissolved in tetrahydrofuran and re-formed after removing the solvent. The covalent bonding was proved by a model reaction of catechol and n-decylamine and occurred through a combination of hydroxylamine reaction and Michael addition reaction. These elastomers exhibit good thermal stability and excellent hydrophobic property and can bond iron sheets to hold the weight of 500 g, indicating their promising as adhesives. These results reveal that TA as a natural product is a suitable “green” crosslinker for the construction of catalyst-free silicone elastomers by a simple crosslinking strategy. Under this strategy, TA and more natural polyphenols could be certainly utilized as crosslinkers to fabricate more organic elastomers by selecting amine-containing polymers and further explore their extensive applications in adhesives, sealants, insulators, sensors, and so forth.

One-Pot Synthesis of Al-P-O Catalysts and Their Catalytic Properties for O-Methylation of Catechol and Methanol.

A series of Al-P-O catalysts (Al-xP-O) were prepared using a P123-assisted one-pot method at different P/Al molar ratios and used for O-methylation of catechol and methanol. The influences of the P/Al molar ratio and P123 addition on catalyst structure and surface acid-base characteristics were investigated in detail. Increasing the P/Al molar ratio more favored crystalline aluminophosphate. The P123-assisted Al3+ and PO43− are known to be stabilized through weak steric force so that the formation of crystalline aluminophosphate could be inhibited at higher P/Al molar ratios. The results showed that the prepared Al-P-O catalysts possessed appropriate weak acid and weak base sites, which was beneficial to the reaction of catechol and methanol. The Al-1.1P-O catalyst synthesized with the assistance of P123 exhibited superior catalytic performances, with 52.5% catechol conversion and higher guaiacol selectivity of 97.6%.

One-Pot Multicomponent Coupling Reaction of Catechols, Benzyl Alcohols/Benzyl Methyl Ethers, and Ammonium Acetate toward Synthesis of Benzoxazoles.

The multicomponent coupling reaction of catechol, ammonium acetate, and benzyl alcohol/benzyl methyl ether in the presence of a Fe(III) catalyst precursor afforded benzoxazole derivatives in good to excellent yields. The notable features of this protocol are abundant availability of the catalyst system, large-scale synthesis, high diversity, and high yields of products.

Photoinduced formation of persistent free radicals, hydrogen radicals, and hydroxyl radicals from catechol on atmospheric particulate matter

SummaryCatechol is speculated to be a potential precursor of environmentally persistent free radicals (EPFRs) in the atmosphere. EPFRs absorbed on PM2.5 have attracted public attention because their toxicity is similar to cigarette smoke. In this study, we found that catechol could produce EPFRs, which were oxygen-centered phenoxy and semiquinone radicals. These free radical species had half-lives of up to 382 days. CaO, CuO, and Fe2O3 markedly promoted EPFR formation from catechol. The valence states of Cu and Fe changed during the photochemical reactions of catechol but no valence state changed for Ca. Alkaline nature of CaO is possibly the key for promoting the free radical formations through acid-base reactions with catechol. In addition to hydroxyl free radicals, hydrogen free radicals and superoxide anions formed from the photochemical reactions of catechol were first discovered. This is of concern because of the adverse effects of these free radicals on human health.

Formation of environmentally persistent free radicals from thermochemical reactions of catechol

In many anthropogenic activities, catechol as a widespread organic chemical could be released and also environmentally persistent free radicals (EPFRs) can be unintentionally formed. However, the underlying links between EPFRs and the role of catechol as an important precursor are not well understood. In this study, EPFR formation from catechol during heating was monitored online by electron paramagnetic resonance spectroscopy. It was found that catechol can produce significant amounts of EPFRs via thermochemical reactions. The EPFR species formed from catechol on metal oxides were oxygen-centered phenoxy and semiquinone radicals. Their half-lives were evaluated to be in the range of 113–909 h. The promotional effects of CaO and CuO on EPFR formation from catechol were stronger than that of Fe2O3. The promotional abilities and underlying mechanisms of various metal oxides in EPFR formation were clarified by X-ray photoelectron spectroscopy. Significant EPFR formation was observed during the cooling stage of a heating reaction system when CaO was used as the reaction medium. The obtained knowledge on the formation of EPFRs from catechol and the key factors involved will enable better control of the formation of EPFRs from anthropogenic activities.

New Pyrazole-Based Ligands: Synthesis, Characterization, and Catalytic Activity of Their Copper Complexes

The purpose of this study is to demonstrate the synthesis of pyrazole-based ligands and to evaluate their catalytic properties in the oxidation reaction of catechol to o-quinone. The ligands were prepared via the condensation of (3,5-dimethyl-1H pyrazol-1-yl)methanol A with the appropriate primary amine. Four pyrazole-based ligands were successfully synthesized and characterized. These ligands provide one pyrazole sp2-nitrogen, one pyridine sp2-nitrogen, and one amine sp3-nitrogen, which were capable of coordinating to the metal. For evaluating the catalytic activity, the experiments were tested by varying the type of solvent, metal ion, anion in the metal salt, and ratios of ligands and metal salts. Excellent catalytic activities for the oxidation of catechol to o-quinone were obtained. The copper (II)-based complexes showed better reactions rates than those based on other metals (e.g., nickel, tin, and barium), which was due to the fact that the active catalytic site of the catecholase enzyme has two active sites from the existence of copper (II) ions. The composition ratios of ligands and metal salts as well as the type of anion in the metal salt bring impacts to the formation of complexes. We found also that the type of solvent contributes to the interaction and dilution of reactants in the solvent. This study demonstrated that the present ligands can be used as a model for further developments in catalytic processes relating to catecholase activity.