SYNTHESIS OF POLYCATECHOL WITH ELECTROCHEMICAL ACTIVITY AND ITS PROPERTIES

The electrochemical polymerization of catechol on platinum has been carried out using repeated potential cyclingbetween -0.2 and 1.1 V (versus SCE). The electrolytic solution consisted of 0.2 mol dm-3 catechol, 0.5 mol dm-3 NaCl and0.1 mol dm-3 Na2HPO4 with pH 8.72. Catechol can not be polymerized at pH ≥ 10.12. Polycatechol has an electrochemicalactivity at pH ≤ 4. The anodic and cathodic peak potentials of polycatechol shift towards more negative values as the pH ofthe solution increases from 1 to 4. The electrochemical activity of polycatechol hardly changes in this pH region, but itdecreases slowly with time. This is caused by oxygen in air, which leads to an irreversible oxidation of polycatechol. Thisproperty is favorable for protecting metals from corrosion. Raman and FTIR spectra of polycatechol and catechol are quitedifferent. AFM images of polycatechol films provide evidence that the image of the oxidized state of polycatechol ismarkedly different from that of the reduced one. This difference is caused by doping and dedoping of polycatechol.

Fluorescence quenching method for the determination of catechol with gold nanoparticles and tyrosinase hybrid system

The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10^(-7)-1.0×10^(-3) mol L^(-1) and a detection limit 1.0×10^(-7) mol L^(-1) of catechol were obtained.o-Quinone intermediate produ...

Hydroxylation Reaction of Phenol to Catechol on Lanthanide-Zirconia Catalyst

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The Effects of Oxidation States, Spin States and Solvents on Molecular Structure, Stability and Spectroscopic Properties of Fe-Catechol Complexes: A Theoretical Study

In this study, in order to explain the solvent and spin state effects on the molecular structure of catechol-Fe complex [Fe(cat)3]n﹣?where n = 2 and 3, Hartree Fock (HF)-Density Functional Theory (DFT) hybrid calculations are performed at the B3LYP/6-311g(d,p) level of theory. The binding energies of Fe2+ and Fe3+ in high-spin state are higher than intermediate and low-spin states which show that the complex formation in a high spin state is more favorable. The calculated binding energies at different solvents indicate that the binding energies in polar solvents are lower than non-polar solvents. Furthermore, spectroscopic studies including FTIR and Raman spectrum in various solvents reveal that the formation of intermolecular bonds between the oxygen atom of carbonyl group and the hydrogen atom of solvent causes a spectral red shift. The calculated FTIR and geometry parameters are in good agreement with previous experimental data. Donor-acceptor interaction energies are evaluated due to the importance of the charge transfer in the complex formation. It is observed that the free electrons of oxygen atom interact with the antibonding orbitals of the iron. Finally, some correlations between the quantum chemical reactivity indices of the complexes and solvent polarity are considered. The study indicates a linear correlation between chemical hardness and binding energies of [Fe(cat)3]3﹣?complex.

Subcloning and high level expression of xylE gene coding for the catechol 2, 3 dioxygenase in E. coli

To construct a high-level expression of xylE gene in E. coli for quick detection of environmental pollution of aromatic compounds. Methods and Results: XylE gene coding for the catechol 2, 3 dioxygenase (CatO2ase ) was amplified from the recombinant plasmid pTG402 by using PCR technique and was subcloned into pUC118N and pUC119N. The single stranded recombinant phage DNA from the transformed E. coli MV1184 cells was used for sequencing. The sequence of xylE gene was proved to be the same as reported. The gene was then subcloned into the high expression plasmid pJLA503, its expression amount being about 34. 2% of the total bacterial proteins. Conclusion: xylE gene is highly expressed in host E. coli TG1.

Nonheme Oxovanadium(Ⅴ,Ⅳ) Complexes Catalyze the Oxidative Cleavage of Catechols

It was found that the oxovanadium(V) complex of triethanolamine (TEA) exhibits catalytic activity to the oxidative cleavage of catechols. On the other hand. the vanadyl nitrilotriacetic acid (NTA) complex is inactive. but leads to the formation of stable ternary complex. The main products of the catalytic oxidative cleavage of 3.5-di-tert-butylcatechol were separated and characterized. Based on the results. a reaction mechanism was

Electrochemical determination of catechol in tea samples using anthraquinone modified carbon paste electrode

Electrochemical investigation of catechol using square wave voltammetry with anthraquinone modified carbon paste electrode was found to be very sensitive. Compared with the unmodified carbon paste electrode, the anthraquinone modified electrode remarkably increases the peak currents of catechol, and greatly lowers the peak potential separation. Two varieties of tea, namely green, and black variety: Wush Wush tea, from Ethiopia, known by its brand name were investigated. Responses for the extracts using ethanol: water (1:4) % v/v showed green tea to be superior in catechol content. Optimization of different variables such as pH of working solution, modifier composition and square wave parameters such as frequency, amplitude and step potential were made to improve the method efficiency during the experiment. The reproducibility for the nine repeated analysis of 80 μmol·L-1 of catechol gave a relative standard deviation of 3.65% and linear calibration plots were obtained in the range 6 to 80 μmol·L-1 with (R = 0.998) and the detection limit with (S/N = 3) was as low as 2.155 x 10-7 mol·L-1.

Relationships between Species of Dyestuff Precursor and Dyeability in Hair Colouring Made by Enzymatic Oxidation Technique Using Bio-Catechols

In the study, hair colouring by utilising enzymatic oxidation of nine species of bio-catechols, which are biobased materials having the catechol (o-dihydroxybenzene) group, was examined. The bio-catechols used are (+)-catechin (Cat), (-)-epicatechin (EC), L-3,4-dihydroxyphenylalanine (DOPA), hematoxylin (HX), brazilin (BZ), rosmarinic acid (RA), caffeic acid (CA), chlorogenic acid (ChA) or ellagic acid (EA). The dyeability of human white hair samples dyed by two kinds of dyeing methods using the bio-catechols was compared. First one is dyeing hair during the enzymatic oxidation of a bio-catechol dye precursor in a dye solution (simultaneous oxidation dyeing method). Second one is dyeing hair by oxidising enzymatically the precursor on hair, which is pre-treated with a bio-catechol solution (post-oxidation dyeing method). The results show that the bio-catechols except EA are oxidised to give colourants and Cat, EC, DOPA, HX and BZ are available for hair dyeing. Overall, the dyeability of simultaneous oxidation dyeing method is higher than that of post-oxidation one. The colour of the hair dyed by simultaneous method is yellowish brown for Cat or EC, grey for DOPA, dark yellowish brown for HX or reddish brown for BZ, respectively. The most vivid or deepest colour of dyed hair is obtained by dyeing with Cat or HX, respectively, in the simultaneous technique. It was found that the bio-catechols having chroman (3, 4-dihydro-2H-1-benzopyran) structure in the molecule such as Cat, EC, HX and BZ are useful for hair colouring.

Association of adverse effects with monoamine oxidase type B inhibitor and catechol-o-methyl transferase inhibitor combination therapy in Parkinson’s disease patients

Currently, levodopa is the most effective and commonly used medication to control motor symptoms in Parkinson’s disease (PD). However, its long-term use is associated with adverse effects (AEs). Combination therapy of a monoamine oxidase type B inhibitor (MAOBI) with levodopa or a catechol-O-methyl transferase inhibitor (COMTI) with levodopa provides benefits to PD patients. Direct comparison of efficacy and side effect profiles is complex. The aim of this study is to investigate the different AE profiles of MAOBI and COMTI combination therapies. Data used to analyze the AEs of different PD medications were retrieved from “The Boston University Medical Center’s Parkinson’s Disease and Movement Disorder Database”. Ten categories of AEs were compared between patients receiving MAOBI and COMTI combination treatment. In total, 87 subjects were included in the analysis. Out of ten AEs, the presence of dementia was signifi- cantly different between the MAOBI and COMTI groups with an OR of 6.9 (COMTI vs MAOBI, 95% CI 1.3 - 37.0). Motor fluctuations were also found to be differently distributed in the two medication groups with an OR of 3.1 (COMTI vs MAOBI, 95% CI 1.0 - 9.8). In this retrospective database analysis of patients treated with combination treatment for PD, combination therapy of a COMTI with levodopa was more likely to be associated with dementia and motor fluctuations than a MAOBI with levodopa.

The Separation of Catechol from Carbofuran Phenol by Extractive Distillation

在这研究，引得出的蒸馏被使用了用高纯净和产量从 carbofuran 酚(CFP ) 分开儿茶酚(猫) 。到猫的 CFP 的相对轻快被测量，并且分开代理人的选择被调查。试验性的结果显示 CFP/CAT 是有在 93.40 &#xb0 的一个 azeotropic 点的一个 azeotropic 系统； C/0.400 kPa 和包含 49.96% CFP 和 50.04% 猫的 azeotropic 混合物。从相对轻快的决心的数据显示出那分开象 diglycol 那样的代理人， 4-butylcatechol (4-TBC ) 能增加相对轻快直到 1.90。在一射击过程批有 3% 的 CFP 混合的引得出的蒸馏(由质量) 分别地，当没有分开代理人的蒸馏提供了纯净和收益时， diglycol 作为分开获得的 CFP 的代理人，纯净和产量是 99.0% 和 95.0% 仅仅 98.0% 和 90.0% 分别地。没有剩余，分开在产品发现的代理人。

Alkylation of Catechol with tert-Butyl Alcohol Catalyzed by Mesoporous Acidic Montmorillonite Heterostructure Catalysts

The liquid phase alkylation of catechol with tert-butyl alcohol to produce 4-tert-butyl catechol (4-TBC) was carried out over MCM-41, HZSM-5, H-exchanged montmorillonite and novel acidic porous montmorillonite heterostructures (PMHs). Upon all catalysts tested, 4-TBC is the main product and 3-tert-butyl catechol (3-TBC) and 3,5-di-tert-butyl catechol are the side products. The synthetic PMHs showed higher conversion of catechol and better selectivity to 4-TBC compared to other solid acid catalysts tested. Over the PMHs derived from H-exchanged montmorillonite through template extraction processes, the suitable reaction temperature is ca 410 K, the ratio of catechol to tert-butyl alcohol is 1:2. Increasing the amount of catalyst (lower weight hourly space velocity) can improve the conversion of catechol and influence the selectivity slightly. The reasonable reaction time is ca 8 h.The type and strength of acidity of H-montmorillonite and PMH were determined by pyridine adsorption FT-IR and ammonia temperature-programmed desorption techniques. The medium and strong acid sites are conducive to producing 4-TBC and the weak acid sites to facilitating the 3-TBC formation. The differences between the PMHs from calcination and those fi'om extraction are attributed to proton migration and acidity change in the gallery surface.

Characterization and Catalytic Activity of Titanium-containing Aluminum Phosphate Prepared by Sol-gel and Nonuniform Precipitation for O-Alkylation of Catechol with Ethanol

Three titanium-containing aluminum phosphate catalysts with a general formula Al 0.77 Ti 0.23 PO 4 were prepared by the sol-gel method at room temperature(APTS), and a nonuniform precipitation procedure at room temperature(APTR) and under reflux(APTF), respectively. The structural features and the surface properties of the three catalysts were determined by means of the physical adsorption of nitrogen at liquid N 2 temperature, XRD, UV-Vis, NH 3-TPD and IR of adsorbed pyridine. The vapor phase O-alkylation of catechol with ethanol over the prepared catalysts was studied. It was found that the activity and the selectivity of these catalysts are greatly dependent on the preparation method, and catalyst APTF shows the highest activity and selectivity. The characterization evidence indicates that the weak Brnsted acid sites were more effective for the reaction.

Vapour-phase O-methylation of Catechol with Methanol on Ti-containing Phosphate Catalysts

Ti-containing phosphate(Ti-P-O) catalysts with different molar ratios of P to Ti(0—2.0) were synthesized and characterized by XRD, N_ 2 -adsorption/desorption, IR and temperature-programmed desorption(TPD) methods. The catalytic properties of Ti-P-O samples in the vapor-phase O-methylation of catechol with methanol were also studied. The catechol conversion increases with the increase of the molar ratio of P to Ti in a range of 0—0.33, while a further increase in the P content leads to a decrease of the catalytic activity. Meanwhile, the selectivities of the catalysts to the main product(guaiacol) increase gradually with the increase of the molar ratio of P to Ti. The presence of relatively strong Lewis acidic and/or basic sites in the P-free catalyst should be responsible for the formation of C-alkylation products. The weak acid-base characteristics of the catalysts are favourable for the mono-O-methylation of catechol. In comparison with the Lewis acidic sites, the Brnsted acidic sites on the catalysts are more active for the title reaction.

Adsorption of catechol from aqueous solution by aminated hypercrosslinked polymers

Adsorption of catechol from aqueous solution with the hypercrosslinked polymeric adsorbent NDA-100 and its derivatives AH-1, AH-2 and AH-3 aminated by dimethylamine, the commercial resin Amberlite XAD-4 and weakly basic anion exchanger resin D301 was compared. It was found that the aminated hypercrosslinked resins had the highest adsorption capacities among the tested polymers. The empirical Freundlich equation was successfully employed to describe the adsorption process. Specific surface area and micropore structure of the adsorbent, in company with tertiary amino groups on matrix affected the adsorption performance towards catechol. In addition, thermodynamic study was carried out to interpret the adsorption mechanism. Kinetic study testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate and increase the adsorption apparent activation energy.

A DFT Study on Intramolecular Hydrogen Bond in Substituted Catechols and Their Radicals

Density functional theory (DFT) at B3LYP/6-31G(d,p) level was employed to calculate intramolecular hydrogen bond enthalpies (HIHB), O-H charge differences, O-H bond lengths and bond orders for various substituted catechols and their radicals generated after H-abstraction. It was found that although the charge difference between hydrogen-bonded H and O played a role in determining HIHB, HIHB was mainly governed by the hydrogen bond length. As the oxygen-centered radical has great tendency to form a chemical bond with the H atom, hydrogen bond lengths in catecholic radicals are systematically shorter than those in catechols. Hence, the HIHB for the former are higher than those for the latter.

Synthesis and Characterization of Model Complexes of Catechol Dioxygenases Supported by the Anionic Hydrotris-3,5-dimethyl-pyrazolylborate Ligand

An iron(Ⅲ) complex [FeIII(TpzMe2)(HpzMe2)Cl2](1) has been synthesized at a low temperature,which contains tripodal ligand,namely,the anionic hydrotris-3,5-dimethyl-pyrazolylborate(TpzMe2). A series of iron(Ⅲ) catecholate complexes 2―5 has been obtained via the reaction of compound 1 with catecholate or substituted catecho-lates. These complexes were characterized by X-ray crystallographic analysis,mass spectrometry and elemental analysis,and the results show that TpzMe2 ligand has the beneficial effect on the stabilization of iron(Ⅲ) catecholate complexes.

Catechol-Bisphosphonate Conjugates: New Potential Chelating Agents for Metal Intoxication Therapy

In a quest for better chelating therapy drugs for the treatment of intoxication by Fe, A1, or actinides, two new series of mixed catechol-bisphosphonate through amide linkage were synthesized. Benzyl group was used as protecting group to avoid the breakage of amide by acid hydrolysis or imcomplete reaction in silylation-dealkylation using bromotrimethylsilane.

Synthesis, Crystal Structure and Catechol Oxidase Mimic Activity of a Dinuclear Copper Complex

A dinuclear copper complex [Cu2LCl2](ClO4)2(L = 2,2'-(piperazine-1,4-diyl)bis-(N,N-bis(pyridine-2-ylmethyl)ethan-1-amine)) has been synthesized and structurally characterized. It crystallizes in triclinic, space group P1 with a = 8.5707(9), b = 10.5083(12), c = 11.4878(13), α = 76.197(2), β = 88.271(2), γ = 87.855(2)o, V = 1003.81(19)3, Z = 1, F(000) = 478, Dc = 1.544 Mg/m3, Mr = 933.60, μ = 1.383 mm-1, the final R = 0.0669 and wR = 0.1486 for 3675 observed reflections with I > 2ρ(I). Its catechol oxidase mimic activity was studied spectroscopically by using 3,5-di-tert-butylcatechol(3,5-DTBC) as the substrate. The results showed that the kinetics of catechol catalyzed by the complex accorded with the Michaelis-Mentent equation, and the catechol oxidase catalytic activity of the complex increased with increasing the pH values.