- Titanosilicate molecular sieve for size-screening photocatalytic conversion
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Titanosilicate molecular sieves, when activated by ultraviolet light irradiation in water in the presence of molecular oxygen, catalyze a conversion of molecules having a size close to the pore of the catalysts but are inactive for molecules having much larger or smaller size. This unprecedented size-screening photocatalytic activity is triggered by a combination of H2O-induced shortened lifetime of active species (charge-transfer excited state of tetrahedrally coordinated titanium oxide) and restricted diffusion of a molecule inside the pore. This catalytic property demonstrates a potential utility of the catalyst for selective transformation of molecules that is associated with a size reduction of molecules, so-labeled molecular shave transformation. Copyright
- Shiraishi, Yasuhiro,Saito, Naoya,Hirai, Takayuki
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Read Online
- Metabolism of halohydroquinones in Rhodococcus chlorophenolicus PCP-1
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The actinomycete Rhodococcus chlorophenolicus PCP-1 metabolises pentachlorophenol into ultimate inorganic end products via tetrachloro-p-hydroquinone. This intermediate was further dehalogenated in the cytoplasm requiring reductant in the cell free system. Tetrafluoro-p-hydroquinone and tetrabromo-p-hydroquinone were also dehalogenated. Chlorophenol analogs, thiol blocking agents and molecular oxygen inhibited the activity. The dehalogenating reactions led to 1,2,4-trihydroxybenzene, which was further metabolized into maleic acid.
- Uotila, J. S.,Kitunen, V. H.,Coote, T.,Saastamoinen, T.,Salkinoja-Salonen, M.,Apajalahti, J. H. A.
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Read Online
- Antagonistic activity of hydroxycoumarin-based antioxidants as possible singlet oxygen precursor photosensitizers
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Coumarins are phenolic-type compounds with efficient antioxidant activity due to their ability to scavenge reactive oxygen species. Nevertheless, their ability to behave as photosensitizers capable of generating reactive oxygen species, such as singlet oxygen, has been less studied. In this work, the photosensitizing ability of seven hydroxycoumarins was evaluated through the photooxidation of ergosterol by quantifying the conversion of ergosterol into ergosterol peroxide. In our experimental conditions, we found that almost every tested antioxidant coumarin promotes the peroxidation of ergosterol. The results suggest that the hydroxycoumarins exhibit potential photosensitizing activity by promoting singlet oxygen generation by a Type II photochemical mechanism. Density functional theory (DFT) calculations were also performed to obtain further insight into the chemical reactivity of tested compounds; the observed tendency in the group of antioxidant coumarins to promote the reaction was their hardness due to the principle of maximum hardness. To evaluate our conclusion, we performed the reaction using a highly polarizable coumarin as a photosensitizer, which resulted in an increased photosensitizing capacity supported with DFT calculations, which reinforces our analysis. Finally, we found that hydroxycoumarins can be potentially pro-oxidants since some of them can act as photosensitizers and generate singlet oxygen in the presence of UV–Vis light, a characteristic that must be considered when these compounds are used as antioxidants.
- Guerrero, Tomás,Vázquez-Ortega, Fernanda,Lagunes, Irene,Ortiz-Blanco, Erik,Sosa-Ortiz, Gabriela,Tovar-Miranda, Ricardo,Medina, Manuel E.,Trigos, ángel
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- Mannich bases of hydroxycoumarins: Synthesis, DFT/QTAIM computational study and assessment of biological activity
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The synthesis of six Mannich bases derived from hydroxycoumarins was carried out in moderate yields, two of these derivatives were described for the first time. Conformational analysis was performed through DFT theoretical calculations explaining the formation of stable six membered rings based on intramolecular hydrogen bonds within the structure. These findings were correlated with the antiproliferative activity. The biological activity of the Mannich bases through their antiproliferative activity in the HeLa cancer cell line is described for the first time, showing that the compounds were able to inhibit proliferation in cervical cancer by more than 60%. Likewise, the theoretical modeling of the photophysical properties was realized with promising results, showing that the HOMO-LUMO energies of the new compounds present the lowest electronic gap values for those with donor groups in their structure, which makes them potential fluorophores. This journal is
- Castro, María Eugenia,Durand-Niconoff, J. Sergio,Fernández-Pomares, Cynthia,Guerrero, Tomás,Juárez-Aguilar, Enrique,Melendez, Francisco J.,Montoya-Hernández, Eva Luz,Olivares-Romero, José L.,Ortiz-Blanco, Erik,Sosa-Ortiz, Gabriela,Tovar-Miranda, Ricardo
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p. 31260 - 31271
(2021/11/30)
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- Preparation method of sesamol
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The invention belongs to the technical field of compound synthesis, and particularly relates to a preparation method of sesamol, which firstly prepares 2 -chloro -1, 4 -diphenol, and then 2 - chlorine -1, 4 -biphenol and sodium hydroxide in an aqueous solution to obtain the sesamol, namely 1 2, 1 2 4 - 4 -triphenol and dichloromethane. The invention provides a new method for preparing the sesame phenol, and the yield of the sesamol is remarkably improved.
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- Enhanced nonradical catalytic oxidation by encapsulating cobalt into nitrogen doped graphene: highlight on interfacial interactions
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Supported metal catalysts are widely used for heterogeneous catalytic processes (e.g., Fenton-like reaction), but the mechanisms of interfacial processes are still ambiguous. Herein, unique nanocarbon based catalysts with Co nanoparticles encapsulated in
- Yu, Xiaoyong,Wang, Lijing,Wang, Xin,Liu, Hongzhi,Wang, Ziyuan,Huang, Yixuan,Shan, Guoqiang,Wang, Weichao,Zhu, Lingyan
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supporting information
p. 7198 - 7207
(2021/03/29)
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- Synthesis of renewable C-C cyclic compounds and high-density biofuels using 5-hydromethylfurfural as a reactant
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The major challenge in the synthesis of high-density biofuels is to identify the bio-based source for C-C cyclic compounds and C-C coupling reactions with a suitable selectivity. Herein, we selectively synthesize 1,2,4-benzenetriol (BTO) with a yield of 51.4% from cellulose-derived 5-hydromethylfurfural via a ring-rearrangement reaction. The cellulose-derived route is a more meaningful route for the C-C cyclic compounds compared to the traditional hemicellulose- and lignin-derived routes. Furthermore, BTO is very easily dimerized via a C-C oxidative coupling reaction, showing a yield of 94.4% and selectivity of nearly 100% under environmentally friendly reaction conditions. After hydrodeoxygenation, bicyclohexane is obtained with a yield of 87.4%. This work not only provides a promising route to produce C-C cyclic fine compounds based on a cellulose-derived route, but also shows a highly efficient synthesis route for high-density biofuels via the C-C oxidative coupling reaction.
- Cai, Taimei,Deng, Qiang,Deng, Shuguang,Gao, Rui,Peng, Hailong,Wang, Jun,Zeng, Zheling,Zhong, Jin,Zou, Ji-Jun
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p. 2468 - 2473
(2020/05/14)
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- Br?nsted Acid Catalyzed Tandem Defunctionalization of Biorenewable Ferulic acid and Derivates into Bio-Catechol
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An efficient conversion of biorenewable ferulic acid into bio-catechol has been developed. The transformation comprises two consecutive defunctionalizations of the substrate, that is, C?O (demethylation) and C?C (de-2-carboxyvinylation) bond cleavage, occurring in one step. The process only requires heating of ferulic acid with HCl (or H2SO4) as catalyst in pressurized hot water (250 °C, 50 bar N2). The versatility is shown on a variety of other (biorenewable) substrates yielding up to 84 % di- (catechol, resorcinol, hydroquinone) and trihydroxybenzenes (pyrogallol, hydroxyquinol), in most cases just requiring simple extraction as work-up.
- Bal, Mathias,Bomon, Jeroen,Liao, Yuhe,Maes, Bert U. W.,Sels, Bert F.,Sergeyev, Sergey,Van Den Broeck, Elias,Van Speybroeck, Veronique
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supporting information
p. 3063 - 3068
(2020/02/05)
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- CONCERTED PROCESSES FOR FORMING 1,2,4-TRIHYDROXYBENZENE FROM HYDROQUINONE
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Flow batteries incorporating an active material with one or more catecholate ligands can have a number of desirable operating features. Commercial syntheses of catechol produce significant quantities of hydroquinone as a byproduct, which presently has limited value in the battery industry and can represent a significant waste disposal issue at industrial production scales. Using a concerted, high-yield process, low-value hydroquinone can be transformed into high-value 1,2,4-trihydroxybenzene, which can be a desirable ligand for active materials of relevance in the flow battery industry. Methods for forming 1,2,4-trihydroxybenzene can include: oxidizing hydroquinone in a first reaction to form p-benzoquinone, converting the p-benzoquinone in a second reaction to form 1,2,4-triacetoxybenzene, deacetylating the 1,2,4-triacetoxybenzene in a third reaction to form 1,2,4-trihydroxybenzene, and isolating the 1,2,4-trihydroxybenzene after performing the first reaction, the second reaction and the third reaction consecutively.
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- Insight into sulfamethoxazole degradation, mechanism, and pathways by AgBr-BaMoO4 composite photocatalyst
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A composite photocatalyst, AgBr-BaMoO4 was fabricated by two step method; microwave hydrothermal and precipitation-deposition. The as prepared photocatalyst samples were characterized by various techniques. The facet coupling was seen between the (204) plane of BaMoO4 and (200)/(222) planes of AgBr on the basis of XRD/HRTEM analysis. The pharmaceutical pollutant, sulfamethoxazole was adopted to investigate the photocatalytic performances of samples under UV–vis irradiation. The AgBr-BaMoO4 composite degraded the aqueous sulfamethoxazole drug in UV–vis light about 64% within 75 min, which was attributed to efficient separation of photogenerated electron–hole pairs across the interface between Ag/AgBr and BaMoO4. The multi-electron induced oxygen reduced reaction (ORR) was observed. The radical trapping experiment indicates that OH? has major role for sulfamethoxazole degradation. The four successive photodegradation of sulfamethoxazole in UV–vis light indicates the stability of composite photocatalyst. Furthermore, the three different degradation pathways were designed on the basis of retention time and molecular masses of 18 degraded organic fragments that was confirmed by high-performance liquid chromatography photodiode array (HPLC-PDA) and high resolution-quadruple time of flight electrospray ionization mass spectroscopy (HR-QTOF ESI/MS) techniques. The total organic carbon (TOC) analysis suggested the mineralization of SMZ by composite photocatalyst. This study not only demonstrates the enhancement of photocatalytic performance of wide band gap semiconductor by making composite with narrow band gap semiconductor but also detail degradation pathways and mechanisms of sulfamethoxazole.
- Ray, Schindra Kumar,Dhakal, Dipesh,Lee, Soo Wohn
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p. 686 - 695
(2018/07/14)
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- Improving removal of 4-chlorophenol using a TiO2 photocatalytic system with microwave and ultraviolet radiation
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A conventional photocatalytic system is a viable tool to purify wastewaters, whereas poor degradation performance due to diverse pollutants under various conditions still leaves it behind commercial markets. This study aimed to determine the degradation e
- Ki, Seo Jin,Jeon, Ki-Joon,Park, Young-Kwon,Jeong, Sangmin,Lee, Heon,Jung, Sang-Chul
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- Study of the paracetamol degradation pathway that generates color and turbidity in oxidized wastewaters by photo-Fenton technology
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This study aims determining the effect that certain kind of water contaminants have on the changes of turbidity during their oxidation. Phenol is considered by its frequent presence in industrial discharges; meanwhile paracetamol is representative of emerging pollutants of pharmaceutical origin. Quite different results are observed in the turbidity changes during the oxidation of both pollutants that evolve following the kinetics of a reaction intermediate. The analysis of paracetamol and phenol degradation pathways reveals that operating conditions are important in the formation of intermediates that cause turbidity. The maximum turbidity levels are achieved operating at the ratios 12?mol HO? per 100?mg contaminant. However the turbidity generated during the paracetamol oxidation only reaches a third of the intensity achieved with phenol. During the paracetamol degradation, the intermediates causing turbidity are similar to the ones found during the phenol decomposition. These species are generated during the initial minutes of oxidation and possess structures of large size and molecular weight. At the máximum turbidity point, muconic acid and hydroquinone are identified and found to coexist with other compounds such as pyrogallol and resorcinol. Therefore, the path involving metasubstitution would be the main originator of turbidity. It is noteworthy the rapid formation of muconic acid that coexists with resorcinol-like species. These compounds enable the establishment of hydrogen bond interactions that yield supramolecular structures.
- Villota, Natalia,Lomas, Jose M.,Camarero, Luis M.
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p. 113 - 119
(2016/07/19)
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- H2O2 in WEB: a highly efficient catalyst system for the Dakin reaction
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Without using any transition metal catalyst, ligand, base, toxic or hazardous reagent, additives/promoters and organic solvent, green Dakin reactions have been successfully carried out by using H2O2 in a natural feedstock extract. The reaction proceeds in neat 'Water Extract of Banana' (WEB) at room temperature under aerobic conditions in very short reaction times and, therefore, it is an evergreen and environmentally sound alternative to the existing protocols for the Dakin reaction. In our system, the reaction was found to afford excellent yield for the desired product with different electron-withdrawing and electron-donating hydroxylated benzaldehydes.
- Saikia, Bishwajit,Borah, Parinita,Barua, Nabin Chandra
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supporting information
p. 4533 - 4536
(2015/09/15)
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- Polyhedral Pt vs. spherical Pt nanoparticles on commercial titanias: Is shape tailoring a guarantee of achieving high activity?
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As shape tailoring is gaining more attention in the field of photocatalysis, exploration of the impact of noble metal (Pt) nanoparticles' morphology on the activity of TiO2-Pt nanocomposites is inevitable. Spherical and polyhedral Pt nanoparticles have been synthesized by chemical reduction, while Aldrich anatase, Aldrich rutile, and Aeroxide P25 were used as base photocatalysts. The nanocomposites were analyzed using DRS, XRD, and HRTEM to uncover morphological, optical, and structural peculiarities of the composite photocatalysts. The importance of the Pt nanoparticles' geometry was proven at three levels: (i) UV light-driven photodegradation of three model pollutants: phenol, methyl orange, and oxalic acid; (ii) the primary degradation intermediates' evolution profile in the case of phenol degradation; and (iii) photocatalytic H2 production.
- Kovács,Fodor, Sz.,Vulpoi,Schrantz,Dombi,Hernádi,Danciu,Pap, Zs.,Baia
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p. 156 - 167
(2015/09/28)
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- Charge transfer and photocatalytic activity in CuO/TiO2 nanoparticle heterojunctions synthesised through a rapid, one-pot, microwave solvothermal route
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Rapid charge carrier recombination is a major limiting factor over efficiency in many semiconductor photocatalysts. To address this, copper(II) oxide/titanium dioxide (CuO/TiO2) heterojunctions were synthesised through a novel, rapid solvothermal microwave procedure using a low-cost copper precursor and commercial P25 TiO2, taking as little as five minutes to synthesise well-defined CuO nanoparticles onto the host TiO2, achieving an intimate contact. The resultant composites encompass pure CuO particles of approximately 6-7 nm diameter, confirmed by means of high resolution transmission electron microscopy and X-ray photoelectron spectroscopy analysis. Photoelectrochemical water splitting was enhanced by nearly 2 times using the junction, whilst ≈1.6 times enhancement in the photocatalytic mineralisation of a model organic pollutant 2,4-dichlorophenoxyacetic acid (2,4-D) was observed. Furthermore, we studied the initial decomposition mechanism of 2,4-D by means of GC-MS analysis. The increase in catalytic activity, investigated by impedance analysis (Mott-Schottky plots) and photoluminescence spectra, is attributed to photoelectron transfer from the more negative conduction band (CB) of TiO2 to CuO, leaving the photohole on TiO2 to take part in oxidation reactions. This strategy allows for in situ charge separation which facilitates superior photocatalytic activity for both pollutant degradation and water splitting.
- Moniz, Savio J. A.,Tang, Junwang
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p. 1659 - 1667
(2015/06/08)
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- Degradation of p-nitrophenol using CuO/Al2O3 as a Fenton-like catalyst under microwave irradiation
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CuO/Al2O3 was synthesized successfully by the impregnation-deposition method and used as a heterogeneous catalyst in a microwave assisted Fenton-like process (MW/FL). The morphology and physico-chemical properties of the CuO/Al2O3 catalyst were characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis. The degradation of p-nitrophenol (PNP) was investigated by different processes, including microwave irradiation (MW) alone, hydrogen peroxide (H2O2) oxidation under microwave irradiation without the catalyst (MW/H2O2), a Fenton-like (FL) process, a MW/FL process and a thermally-assisted Fenton-like (TH/FL) process. The results showed that the CuO/Al2O3 catalyzed MW/FL could generate more hydroxyl radicals (OH) and remove PNP more effectively compared to other processes. The effects of initial pH, dosage of H2O2 and catalyst, microwave power and radiation time, and PNP concentration on the removal efficiency were also studied. The results showed that 93% removal efficiency of PNP was obtained within 6 min under optimized conditions. Moreover, the catalyst had a good stability and reusability, thus expanding the scope of non-iron based catalysts in the Fenton-like reactions.
- Pan, Weiqian,Zhang, Guangshan,Zheng, Tong,Wang, Peng
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p. 27043 - 27051
(2015/03/30)
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- Oxidative degradation of phenol by corona dielectric barrier discharge at gas-liquid interphase
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In this study, corona gas-liquid dielectric barrier discharge reactor for phenol degradation was investigated. The discharge was formed between two needle metal electrodes and an aqueous solution surface where the counter electrode was submerged and separated by a quartz dielectric tube. Effects of solution conductivity, pH and gas composition on the degradation were examined. Experimental results showed that the degradation of phenol proceeded perfectly in a wide range of solution conductivity. In the process of degradation of phenol, ozone was additionally formed. The removal of phenol increased with the order: argon air oxygen. Increasing pH was favorable for phenol removal. When using argon as the discharge gas, the major degradation products were catechol, hydroquinone, hydroxyhydroquinone, acetic acid, formic acid and oxalic acid. In oxygen or air discharges, 1,4-benzoquinone and muconic acid were additionally formed. The energy efficiency of removal of phenol has been compared with other competitive processes.
- Wang, Lei,Yu, Xin,Li, Guoxin,Li, Dailin
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p. 853 - 859
(2014/06/09)
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- LIGNIN OXIDATION AND PRODUCTS THEREOF
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Provided herein is a method of oxidizing lignin. Further disclosed herein are aromatic and non-aromatic compounds obtained from oxidized lignin.
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Page/Page column 77
(2012/06/16)
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- METHOD FOR PRODUCING POLYHYDRIC PHENOL
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The present invention is a method for producing a polyhydric phenol, including the following steps (a) to (d): (a) a first step of producing (4S,5R,6S)-4,5,6-trihydroxy-2-cyclohexcene-1-one from 2-deoxy-scyllo-inosose by a dehydration reaction; (b) a second step of producing 1,2,4-trihydroxybenzene from the (4S,5R,6S)-4,5,6-trihydroxy-2-cyclohexene-1-one obtained in the first step by a dehydration reaction; (c) a third step of producing 4-hydroxycyclohexane-1,3-dione from the 1,2,4-trihydroxybenzene by a catalytic hydrogenation reaction with the use of a metal catalyst; and (d) a fourth step of producing hydroquinone by heating the 4-hydroxycyclohexane-1,3-dione.
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Page/Page column 12-13
(2012/03/10)
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- Visible light photo-oxidation of model pollutants using CaCu 3Ti4O12: An experimental and theoretical study of optical properties, electronic structure, and selectivity
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Charge transfer between metal ions occupying distinct crystallographic sublattices in an ordered material is a strategy to confer visible light absorption on complex oxides to generate potentially catalytically active electron and hole charge carriers. CaCu3Ti4O12 has distinct octahedral Ti4+ and square planar Cu2+ sites and is thus a candidate material for this approach. The sol-gel synthesis of high surface area CaCu3Ti4012 and investigation of its optical absorption and photocatalytic reactivity with model pollutants are reported. Two gaps of 2.21 and 1.39 eV are observed in the visible region. These absorptions are explained by LSDA+U electronic structure calculations, including electron correlation on the Cu sites, as arising from transitions from a Cu-hybridized O 2p-derived valence band to localized empty states on Cu (attributed to the isolation of CuO4 units within the structure of CaCu3Ti4O12) and to a Ti-based conduction band. The resulting charge carriers produce selective visible light photodegradation of 4-chlorophenol (monitored by mass spectrometry) by Pt-loaded CaCu 3Ti4O12 which is attributed to the chemical nature of the photogenerated charge carriers and has a quantum yield comparable with commercial visible light photocatalysts.
- Clark, Joanna H.,Dyer, Matthew S.,Palgrave, Robert G.,Ireland, Christopher P.,Darwent, James R.,Claridge, John B.,Rosseinsky, Matthew J.
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supporting information; experimental part
p. 1016 - 1032
(2011/04/15)
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- Three-dimensional organotin-hexacyanoferrate polymers as effective oxidizing reagents towards phenols
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Three-dimensional organotin-hexacyanoferrate polymers of the type ∞3[(R3Sn)3Fe III(CN)6] where R = Me (I), n-butyl (II) and phenyl (III), represent members of the family of supramolecular coordination polymers (SCPs) which have zeolitic-like structure containing micropores. The structures of I-III contain wide channels capable of encapsulating resorcinol, which undergoes in situ oxidation to 1,3,4-trihydroxy benzene (THB) or p-nitrophenol (PNP), which converts to 1,4-benzoquinone (BQ) and 2-hydroxybenzoquinone (2-HBQ). The oxidation products were investigated by spectroscopic methods and by HPLC. The SCP III was found to be a more effective oxidizing reagent than I and II due to the presence of terminal Sn-OH2 groups hydrogen bonded to one-sixth of the terminal CN groups, causing more wide expandable channels. In addition, mechanisms of the oxidation processes of resorcinol and PNP have been proposed. Copyright
- Etaiw, Safaa El-Din H.,Werida, Amal H.
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experimental part
p. 805 - 808
(2011/06/20)
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- Synthesis and characterization of mesoporous-TiO2 with enhanced photocatalytic activity for the degradation of chloro-phenol
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Mesoporous-titania (TiO2) photocatalysts have been synthesized using polyethylene glycol (PEG) as a template in dilute acetic acid aqueous solution by hydrothermal process. The effect of PEG molecular weights and thermal treatment on the resultant structure and photocatalytic activity are investigated. Structural and phase compositional properties of the resultant photocatalysts are characterized by transmission electron microscopy, X-ray diffraction and nitrogen sorption analysis. When the molecular weights of PEG vary from 600 to 20,000, the particle sizes of mesoporous structure decrease from 15.1 to 13.3 nm and mean pore sizes increase from 6.9 to 10.6 nm. The chemical reactions of the formation of mesoporous-TiO2 during its synthesis have been proposed and discussed. The activities of mesoporous-TiO2 photocatalysts are evaluated and compared with Degussa P-25 using chloro-phenol as a testing compound. The reaction mechanism of photodegradation is also described on the basis of high performance liquid chromatography.
- Shamaila, Sajjad,Sajjad, Ahmed Khan Leghari,Chen, Feng,Zhang, Jinlong
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experimental part
p. 1375 - 1382
(2010/12/19)
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- PROCESS FOR STRAIGHTENING KERATIN FIBRES WITH A HEATING MEANS AND DENATURING AGENTS
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The invention relates to a process for straightening keratin fibres, comprising: (i) a step in which a straightening composition containing at least two denaturing agents is applied to the keratin fibres, (ii) a step in which the temperature of the keratin fibres is raised, using a heating means, to a temperature of between 110 and 250° C.
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- Light-activated regulation of cofilin dynamics using a photocaged hydrogen peroxide generator
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Hydrogen peroxide (H2O2) can exert diverse signaling and stress responses within living systems depending on its spatial and temporal dynamics. Here we report a new small-molecule probe for producing H 2O2 on demand upon photoactivation and its application for optical regulation of cofilin-actin rod formation in living cells. This chemical method offers many potential opportunities for dissecting biological roles for H2O2 as well as remote control of cell behavior via H2O2-mediated pathways.
- Miller, Evan W.,Taulet, Nicolas,Onak, Carl S.,New, Elizabeth J.,Lanselle, Julie K.,Smelick, Gillian S.,Chang, Christopher J.
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p. 17071 - 17073
(2011/03/01)
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- Studies on the biosynthesis of bovilactone-4,4 and related fungal meroterpenoids
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The initial step in the biosynthesis of suillin (1), boviquinone-4 (2) and bovilactone-4,4 (3) in Suillus species is the geranylgeranylation of 3,4-dihydroxybenzoic acid at the 2-position. Feeding experiments with advanced precursors have identified boviquinone-4 and deacetylsuillin (9) as building blocks for the dilactone and catechol moieties, respectively, of bovilactone-4,4 (3). In order to explain the failure of boviquinone-4 (2) to incorporate side-chain-labelled deacetylsuillin (9#), an alternative sequence for the formation of 2 is proposed. During these experiments an interesting change in metabolism was noticed: after administration of larger quantities of aromatic carboxylic acids, the boviquinone-4 present in the fruit bodies disappeared and de novo synthesis of bovilactone-4,4 occurred. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Lang, Martin,Muehlbauer, Andrea,Jaegers, Erhard,Steglich, Wolfgang
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experimental part
p. 3544 - 3551
(2009/04/08)
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- Kinetics and mechanism of the reactions of ozone with guaiacol, veratrol, and veratrol derivatives
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The kinetics of the reactions of ozone with compounds modeling structural lignin fragments, viz., phenol, guaiacol, veratrol, veratric aldehyde, and veratric alcohol, was studied. The reaction rate constants were calculated using the mass transfer model for the chemical reaction based on the film theory. The rate constants of the reactions of ozone with compounds of the veratryl series were calculated by the Hammett equation. The major ozonation products of the studied compounds were determined by HPLC. The ozonation mechanism was proposed.
- Khudoshin,Mitrofanova,Lunin
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experimental part
p. 283 - 288
(2009/06/05)
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- Novel features in the oxidation of dihydroxy benzenes by 2,6-dichloroquinone-4-chloro-imide in acetic acid and sodium acetate buffer medium
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Kinetics of oxidation of quinol, catechol and resorcinol by 2,6-dichloroquinone-4-chloro-imide (DCQCI) in CH3COOH-NaOAc system is reported. The kinetic features of ortho dihydroxy and para dihydroxy benzenes are similar. The reactions are zero order in oxidant at lower concentrations of oxidant (below 0.0005 M) and fractional order in substrate. At higher concentrations of oxidant, these two compounds exhibit first order in oxidant and fractional order in substrate leading to independence. Resorcinol exhibits different kinetic features: first order in oxidant at all concentrations and fractional order in substrate. The major products are coupling products under these conditions. Reactivity order is resorcinol 〉 catechol 〉 quinol. This result is novel. A mechanism is postulated to explain the observed order and a suitable rate law has been derived.
- Madhavi,Syama Sundar,Radhakrishna Murti
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p. 242 - 245
(2007/10/03)
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- Hydrothermal upgrading of biomass to biofuel; studies on some monosaccharide model compounds
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During the hydrothermal upgrading of biomass, hydrolysis to glucose is an important step. To elucidate some of the reaction pathways that follow this initial hydrolysis, the hydrothermal treatment (340°C, 27.5MPa, 25-204s) of dilute (50mM) solutions of D-glucose and some other monosaccharides were studied. As a result of the increase of Kw under subcritical conditions, both acid and base catalysed reactions occur. The acid catalysed reactions are mainly dehydrations leading initially to 5-hydroxymethylfurfural. Important base catalysed reactions result in glycolaldehyde and glyceraldehyde. Further fragmentations and dehydrations lead to a variety of low molecular weight compounds such as formic acid, acetic acid, lactic acid, acrylic acid, 2-furaldehyde and 1,2,4-benzenetriol. Important pathways leading to a decrease of the O-content of the liquid reaction products start from the intermediate glyceraldehyde, which forms pyruvaldehyde, which in its turn is converted into formic acid and acetaldehyde. The latter compound can also be formed via isomerisation of glyceraldehyde into lactic acid followed by decarbonylation.
- Srokol, Zbigniew,Bouche, Anne-Gaelle,Van Estrik, Anton,Strik, Rob C.J.,Maschmeyer, Thomas,Peters, Joop A.
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p. 1717 - 1726
(2007/10/03)
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- 1,3-Dihydroxybenzene derivatives and colorants containing said compounds
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1,3-Dihydroxybenzene derivatives of general formula (I) or (Ia) or physiologically tolerated, water-soluble thereof wherein R′1 denotes substituted pyridyl group, a pyrimidyl group, a group of formula (IIa) or (IIIa) and the dyeing agents for keratin fibers containing these compounds.
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- One step hair coloring compositions using salts
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A hair coloring composition comprising the following two compositions which are mixed just prior to application to the hair: (a) a composition comprising a water-soluble peroxygen oxidizing agent; and (b) a composition comprising one or more oxidative hair coloring agents selected from the group consisting of an aromatic diamine, an amino phenol, a naphthol, a polyhydric phenol, a catechol and mixtures thereof; wherein the composition comprising one or more oxidative hair coloring agents further comprises al least one water soluble carbonate releasing salts; and optionally a water soluble ammonium salt, is described.
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- Transition metal complexes as dye forming catalysts in hair coloring compositions
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A hair coloring composition comprising a first composition which comprises: (a) a dye forming transition metal salt or complex; which is first applied to the hair; and a second composition which comprises the following two compositions which are mixed just prior to application to the hair: (a) a composition comprising a water-soluble peroxygen oxidizing agent; and (b) a composition comprising one or more oxidative hair coloring agents selected from the group consisting of an aromatic diamine, an aminophenol, a polyhydric phenol a catechol and mixtures thereof.
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- Enhanced color deposition for hair with sequestering agents
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Hair coloring compositions which comprise: (A) non-nitrogenous chelating agents from the group consisting of polyphosphate; phosphonates; hydroxycarboxylates; polyacrylates; zeolite; and mixtures thereof; (B) an oxidative dye primary intermediate; and (C) an oxidative dye coupler; (D) and water are described. The present invention also relates to a method for coloring hair which comprises contacting said hair with a hair coloring composition as described above.
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- Deoxygenation of polyhydroxybenzenes: An alternative strategy for the benzene-free synthesis of aromatic chemicals
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New synthetic connections have been established between glucose and aromatic chemicals such as pyrogallol, hydroquinone, and resorcinol. The centerpiece of this approach is the removal of one oxygen atom from 1,2,3,4-tetrahydroxybenzene, hydroxyhydroquinone, and phloroglucinol methyl ether to form pyrogallol, hydroquinone, and resorcinol, respectively. Deoxygenations are accomplished by Rh-catalyzed hydrogenation of the starting polyhydroxybenzenes followed by acid-catalyzed dehydration of putative dihydro intermediates. Pyrogallol synthesis consists of converting glucose into myo-inositol, oxidation to myo-2-inosose, dehydration to 1,2,3,4-tetrahydroxybenzene, and deoxygenation to form pyrogallol. Synthesis of pyrogallol via myo-2-inosose requires 4 enzyme-catalyzed and 2 chemical steps. For comparison, synthesis of pyrogallol from glucose via gallic acid intermediacy and the shikimate pathway requires at least 20 enzyme-catalyzed steps. A new benzene-free synthesis of hydroquinone employs conversion of glucose into 2-deoxy-scyllo-inosose, dehydration of this inosose to hydroxyhydroquinone, and subsequent deoxygenation to form hydroquinone. Synthesis of hydroquinone via 2-deoxy-scyllo-inosose requires 2 enzyme-catalyzed and 2 chemical steps. By contrast, synthesis of hydroquinone using the shikimate pathway and intermediacy of quinic acid requires 18 enzyme-catalyzed steps and 1 chemical step. Methylation of triacetic acid lactone, cyclization, and regioselective deoxygenation of phloroglucinol methyl ether affords resorcinol. Given the ability to synthesize triacetic acid lactone from glucose, this constitutes the first benzene-free route for the synthesis of resorcinol. Copyright
- Hansen, Chad A.,Frost
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p. 5926 - 5927
(2007/10/03)
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- NON-AQUEOUS, LIQUID, ENZYME-CONTAINING COMPOSITIONS
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A substantially water-free, liquid, enzyme-containing composition comprises: (A) an enzyme; (B) a substance selected from (i) substances which in aqueous medium are substrates for said enzyme, (ii) substances which in aqueous medium are precursors for substrates for said enzyme, and (iii) substances which are cofactors for said enzyme; and (C) a non-aqueous liquid phase.
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- Complete destruction of p-Nitrophenol in aqueous medium by electro-fenton method
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An indirect electrochemical method, which is very efficient for the degradation of organic pollutants in water, is described. The method, named electro-Fenton, is based on electrocatalytical generation of Fenton's reagent to produce hydroxyl radicals, which are very active toward organic compounds. An industrial pollutant, p-nitrophenol (PNP), was chosen for this study and was eventually mineralized. The major intermediary degradation products such as hydroquinone, benzoquinone, 4-nitrocatechol, 1,2,4-trihydroxybenzene and 3,4,5-trihydroxynitrobenzene were unequivocally identified by HPLC and GC-MS methods. The rate constants of the hydroxylation reactions were determined. The mineralization of the initial pollutant and the intermediates formed during electro-Fenton treatment was followed by total organic carbon (TOC) analyses. Dependence of mineralization on the amount of electrical energy consumed is shown by the relative decrease ofTOC values. A mineralization reaction mechanism is proposed. An indirect electrochemical method, which is very efficient for the degradation of organic pollutants in water, is described. The method, named electro-Fenton, is based on electrocatalytical generation of Fenton's reagent to produce hydroxyl radicals, which are very active toward organic compounds. An industrial pollutant, p-nitrophenol (PNP), was chosen for this study and was eventually mineralized. The major intermediary degradation products such as hydroquinone, benzoquinone, 4-nitrocatechol, 1,2,4-trihydroxybenzene and 3,4,5-trihydroxynitrobenzene were unequivocally identified by HPLC and GC-MS methods. The rate constants of the hydroxylation reactions were determined. The mineralization of the initial pollutant and the intermediates formed during electro-Fenton treatment was followed by total organic carbon (TOC) analyses. Dependence of mineralization on the amount of electrical energy consumed is shown by the relative decrease of TOC values. A mineralization reaction mechanism is proposed. The destruction of p-nitrophenol by the electro-Fenton method was examined. The method is based on the oxidation of the substrate by hydroxyl radicals generated in situ in an electrochemically induced Fenton reaction. The progress of all reactions and product distribution were monitored by high-performance liquid chromatography and gas chromatography-mass spectrometry. Results showed that p-nitrophenol disappeared, as did the degradation products after reaching a maximum concentration. The rapid degradation of p-nitrophenol was accompanied by the appearance of aromatic intermediates, such as p-nitrocatechol and hydroquinone. The subsequent decrease in p-nitrocatechol was accompanied by an increase in 1,2,4-trihydroxybenzene, while the decrease in hydroquinone was accompanied by the production of benzoquinone. The mineralization mechanism is described. The variation in TOC values taken at different times during treatment showed their dependence on the charge passed or electrical energy consumed.
- Oturan,Peiroten,Chartrin,Acher
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p. 3474 - 3479
(2007/10/03)
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- An expeditious chemo-enzymatic route from glucose to catechol by theuse of 2-deoxy-scyllo-inosose synthase
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A potential two-step process to catechol from D-glucose comprising one- pot incubation of D-glucose with recombinant 2-deoxy-scyllo-inosose synthase (BtrC) and hexokinase, togther with chemical reductive dehydration of the resulting 2-deoxy-scyllo-inosose with Hl, was developed. (C) 2000 Elsevier Science Ltd.
- Kakinuma, Katsumi,Nango, Eriko,Kudo, Fumitaka,Matsushima, Yoshitaka,Eguchi, Tadashi
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p. 1935 - 1938
(2007/10/03)
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- 2,3-Dioxabicyclo[2.2.2]oct-7-en-5-one: Synthesis and Reactions of the Keto Endoperoxide of Phenol
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The photooxygenation of 1,4-cyclohexadiene (3) affords the diastereomeric hydroperoxy endoperoxides exo-4 and endo-4 and the diastereomeric hydroperoxides trans-5 and cis-5 in a ratio of 87: 9:3.5:0.5. Selective reduction of hydroperoxide group in the endoperoxides exo-4 and endo-4 in the presence of titanium tetraisopropoxide-diethyl sulfide gave the corresponding hydroxy endoperoxides exo-7 and endo-7, which on PCC oxidation leads to the phenol-derived keto endoperoxide 2. The triphenylphosphine deoxygenation of the keto endoperoxide 2 produces a 9:1 mixture of 1,2-and 1,4-dihydroxybenzenes 10 and 11, while the CoTPP-catalyzed rearrangement affords the bisepoxide 12, malealdehyde (13), and β-lactone 14. The mechanisms of these transformations are presented.
- Adam, Waldemar,Balci, Metin,Kilic, Hamdullah
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p. 5926 - 5931
(2007/10/03)
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- Photocatalysis by illuminated titania: Oxidation of hydroquinone and p-benzoquinone
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Photocatalytic oxidation of hydroquinonc and p-benzoquinone, the main intermediates which are formed in the process of phenol oxidation on irradiated titania, was studied. The reaction proceeds via several steps. Some of the intermediates were detected by HPLC and GC-MS: ethanedial, glycerol, and 1,2,4-trihydroxybenzene. Under illumination in the presence of TiO2, p-benzoquinone initially transforms partly to hydroquinone, partly oxidizes to unidentified intermediates. The residue, about 4% of the concentration of hydroquinone, undergoes slow oxidation together with the hydroquinone. The rate of hydroquinone photooxidation shows 1st order behaviour.
- Sobczynski, Andrzej,Duczmal, Lukasz,Dobosz, Anna
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p. 377 - 384
(2007/10/03)
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- Nitration and hydroxylation of substituted phenols by peroxynitrite. Kinetic feature and an alternative mechanistic view
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The reaction of peroxynitrite (ONOO-) with a series of para-substituted phenols has been examined in aqueous phosphate buffer and acetonitrile solutions. Major products were the corresponding 2-nitro derivative and the 4-substituted catechol. Kinetic study showed good correlation with Hammett σ(p)+ parameters and reduction potentials, suggesting the possible one-electron transfer process involving the nitrosoniun ion (NO+) as initial electrophile generated from peroxynitrous acid.
- Nonoyama, Nobuaki,Chiba, Kazuhiko,Hisatome, Kaori,Suzuki, Hitomi,Shintani, Futoshi
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p. 6933 - 6937
(2007/10/03)
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- Syntheses of Cyclic Triphenylantimony(V) Catecholates from Triphenylantimony, tert-Butyl Hydroperoxide, and Polyhydric Phenols
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Cyclic triphenylantimony(V) catecholates are prepared by reactions of triphenylantimony with polyhydric phenols (pyrogallol, hydroxyhydroquinone, and quercetin) in the presence of tert-butyl hydroperoxide. Triphenylantimony reacts with polyhydric phenols selectively at the o-hydroxy groups to give the corresponding Sb(V) derivatives.
- Dodonov,Fedorov,Zaburdyaeva
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p. 1460 - 1462
(2007/10/03)
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- Oxidation of Simple Phenols by a Homobimetallic Cerium(IV)-Calix(8)arene Complex in Conjunction with Hydrogen Peroxide
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Phenolic substrates are regioselectively hydroxylated under mild conditions with a cerium(IV)-calix(8)arene complex.
- Chawla, H. Mohindra,Hooda, Usha,Singh, Veena
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p. 617 - 618
(2007/10/02)
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- Synthesis of 2-acyl-4-hydroxycyclohexane-1,3-diones, kairomones and defensive compounds of some insects
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The synthesis of some natural β-triketones starting from a new synthon, 4-hydroxycyclohexane-1,3-dione, is described including the first preparation of /Z,Z/-2-octadec-9,12-dienoyl-4-hydroxycyclohexane-1,3-dione, kairomone of some species of Lepidoptera.
- Zaitsev, Vladimir G.,Polosov, Genrich I.,Lakhvich, Fyodor A.
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p. 6377 - 6386
(2007/10/02)
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- Phototransformation of resorcinol induced by excitation of nitrite and nitrate ions. II: nitrate ions
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The excitation of nitrate ions in an aqueous solution of resorcinol (I) at pH = 5.5-6.5, leads to a mixture of 1,2,3-trihydroxybenzene (II), 1,2,4-trihydroxybenzene (III), 4-nitrosoresorcinol (V) and 4-nitroresorcinol (VII). A secondary formation of 2, 4-dinitrosoresorcinol (VI) was also detected.
- Machado,Boule
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p. 165 - 173
(2007/10/03)
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- Hydrothermal formation of 1,2,4-benzenetriol from 5-hydroxymethyl-2-furaldehyde and D-fructose
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Thermolysis of 0.05 M aqueous 5-hydroxymethyl-2-furaldehyde (HMF) at 27.5 MPa and 290 to 400°C led to the formation of 1,2,4-benzenetriol in yields of up to 46% at 50% HMP conversion. The reaction temperature and water density have a significant effect on the product composition. Pseudo-first-order reaction rate constants for HMF conversion under these conditions range from 0.107 to 0.308 min-1. For the region 290 to 350°C, the activation energy for HMF conversion was found to be 47.7 kJ.mol-1. When subjecting D-fructose to hydrothermolysis, the main products are HMF, 1,2,4-benzenetriol, and furfural. Thermolysis of 0.05 M aqueous 5-hydroxymethyl-2-furaldehyde (HMF) at 27.5 MPa and 290 to 400°C led to the formation of 1,2,4-benzenetriol in yields of up to 46% at 50% HMF conversion. The reaction temperature and water density have a significant effect on the product composition. Pseudo-first-order reaction rate constants for HMF conversion under these conditions range from 0.107 to 0.308 min-1. For the region 290 to 350°C, the activation energy for HMF conversion was found to be 47.7 kJ.mol-1. When subjecting D-fructose to hydrothermolysis, the main products are HMF, 1,2,4-benzenetriol, and furfural.
- Luijkx,Van Rantwijk,Van Bekkum
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p. 131 - 139
(2007/10/02)
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- Pyrolysis of some (13)C-labeled glucans: A mechanistic study
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An isotopic labeling study has been conducted to investigate the chemical mechanisms involved in the formation of certain pyrolysis products of glucans, specifically glycolaldehyde (GA), acetol (hydroxypropanone), acetic acid, and formic acid, which are the major non-aqueous components of the distillate fraction (-60 deg C condensate) of the pyrolyzate. (13)C labels at C-1, C-2, and C-6 of the glucose rings in synthetic glucans were used to reveal the origins of this compounds.In general, the results show that each compound is formed by several different mechanisms, but suggest that only a few mechanisms predominate in each case.Glycolaldehyde derives predominantly from the C-1-C-2 segment of the glucose monomers, with C-5-C-6 also contributing significantly.Evidence is presented supporting heterolytic mechanisms which require a reducing end-group and base catalysis.Acetol derives mostly from three contiguous carbons that include a terminal carbon (C-1 or C-6), most often C-6 and most often appearing as the methyl carbon in the acetol.Acetic acid also arises most often from terminal carbons, the C-5-C-6 segment being the major source, with the methyl carbon usually deriving from C-1 or C-6.About half of the formic acid produced arises from C-1.Mechanisms derived from the chemistry of alkaline degradation and involving acylformylcarbinol intermediates are proposed.
- Ponder, Glenn R.,Richards, Geoffrey N.
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- A Novel Photo-induced Fenton's Reaction. Perfluorinated Poly(p-Phenylene)-catalyzed Photohydroxylation of Benzene with O2 and H2O to Phenol
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18O Tracer study of perfluorinated poly(p-phenylene)-catalyzed photohydroxylation of benzene to phenol with H218O and 16O2 revealed that the hydroxylation initially occurs by the attack of the hydroxyl radical (H18O radical) generated by the photooxidation of H218O, but the hydroxyl radical (H16O radical) derived from the concurrently produced H216O2 comes to participate in further hydroxylation as the photocatalysis proceeds.
- Maruo, Katsuya,Wada, Yuji,Yanagida, Shozo
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p. 565 - 566
(2007/10/02)
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- Formation of 1,2,4-benzenetriol by hydrothermal treatment of carbohydrates.
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Conversion of dilute aqueous solutions of 5-hydroxymethyl-2-furaldehyde and D-fructose under near-critical conditions led to the formation of 1,2,4-benzenetriol in relatively high yields.
- Luijkx, G. C. A.,Rantwijk, F. van,Bekkum, H. van
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p. 343 - 344
(2007/10/02)
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- Cycloheptaamylose as a model for starch in the pyrolysis of polysaccharides
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The pyrolysis of cycloheptaamylose has been studied as a model for starch. 1,6-Anhydro-β-D-glucopyranose (levoglucosan, LG, 7) and its furanose isomer are major products from vacuum pyrolysis at 280, 300, and 320°, with combined yields ranging from 38 to 50% of the substrate-dependent on temperature. Pyrolysis in methyl sulfoxide at 150° produced LG and glucose as well as gluco-oligosaccharides of d.p. up to 7, with both reducing and 1,6-anhydro end-groups. A mechanism is postulated in which the first step is the heterolytic scission of a glucosidic linkage to form a linear, seven-membered oligosaccharide having a glucosyl cation in place of the reducing end-group. The cation is stabilized either by intramolecular attack of O-6 on the C-1 cation or by intermolecular transglycosylation. The former product subsequently yields LG upon scission of a terminal glucosidic linkage. The pyrolysis of cycloheptaamylose has been studied as a model for starch. 1,6-Anhydro-β-D-glucopyranose (levoglucosan, LG, 7) and its furanose isomer are major products from vacuum pyrolysis at 280, 300, and 320°, with combined yields ranging from 38 to 50% of the substrate dependent on temperature. Pyrolysis in methyl sulfoxide at 150° produced LG and glucose as well as gluco-oligosaccharides of d.p. up to 7, with both reducing and 1,6-anhydro end-groups. A mechanism is postulated in which the first step is the heterolytic scission of a glucosidic linkage to form a linear, seven-membered oligosaccharide having a glucosyl cation in place of the reducing end-group. The cation is stabilized either by intramolecular attack of O-6 on the C-1 cation or by intermolecular transglycosylation. The former product subsequently yields LG upon scission of a terminal glucosidic linkage.
- Lowary,Richards
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p. 157 - 166
(2007/10/02)
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- Flash Photolysis-HPLC Method applied to the Study of Photodegradation Reactions
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A new method, involving UV flash photolysis followed shortly by HPLC analysis of products, has been applied to the study of the partial photooxidation of 4-chlorophenol as an example of an oxidative photodegradation reaction of pollutants.
- Lipczynska-Kochany, Ewa,Bolton, James R.
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p. 1596 - 1597
(2007/10/02)
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- A NEW SYNTHESIS OF 1,2,4-BENZENETRIOL CONGENERS
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1,2,4-Benzenetriols were synthesized via 4,4-bis(ethylthio)-1,3-cyclohexanediones which were prepared by means of two types of Michael-Claisen condensation starting from methyl bis(ethylthio)acetate or 1,1-bis(ethylthio)-2-propanone.Keywords- annelation; aromatic synthesis; 1,2,4-benzenetriol; methyl bis(ethylthio)acetate; 1,1-bis(ethylthio)-2-propanone; C2+C4 annelation; C3+C3 annelation; Michael-Claisen condensation; α,β-unsaturated ester; dibenzofurandiol
- Ozaki, Yutaka,Kim, Sang-Won
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p. 304 - 307
(2007/10/02)
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