- Copper/iron-catalyzed Ullmann coupling of diiodo- and dibromoarenes and diphenols for the synthesis of aryl ether macrocycles
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Diiodoarenes (or dibromoarenes) reacted with diphenols, catalyzed by CuI/Fe(acac)3 in the presence of K2CO3 in anhydrous DMSO at 110°C for 7 days under nitrogen atmosphere, to afford macrocyclic aryl ethers effectively. To expand this methodology, a cyclic hepta(p-phenylene oxide) and cyclic deca(p-phenylene oxide) were synthesized in one pot. Some macrocyclic aryl ethers showed strong fluorescence in acetone at 25°C.
- Zhou, Qizhong,Su, Liangjun,Jiang, Tiansheng,Zhang, Bin,Chen, Rener,Jiang, Huajiang,Ye, Yuyuan,Zhu, Mengqing,Han, Deman,Shen, Jianfen,Dai, Guoliang,Li, Zhanting
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- RADIOLYSIS OF POLYCHLORODIBENZODIOXINS IN HEXANE
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In the radiolysis of 2,3,7,8-tetrachlorodibenzodioxin in n-hexane (dose 6.5 Mrad), the degree of its decomposition according to data of chromatography-mass spectrometry is not less than 99.99995 rel. percent (detection limit 2E-10 mass percent).In this case, the less-chlorinated dibenzodioxins formed at lower irradiation doses are not detected.
- Mitroshkov, A. V.,Revel'skii, I. A.,Podsoblyaev, A. P.,Egorov, V. V.,Kostyanovskii, R. G.
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- Mechanisms of dioxin formation from the high-temperature oxidation of 2-chlorophenol
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The homogeneous, gas-phase oxidative thermal degradation of 2-chlorophenol was studied in a 1 cm i.d., fused silica flow reactor at a concentration of 88 ppm, reaction time of 2.0 s, over a temperature range of 300 to 1000 °C. Observed products in order of yield were as follows: 4,6-dichlorodibenzofuran (4,6-DCDF) > dibenzo-p-dioxin (DD) > 1-monochlorodibenzo-p-dioxin (1-MCDD), 4-chlorodibenzofuran (4-MCDF), dibenzofuran (DF), naphthalene, chloronaphthalene, 2,4-dichlorophenol, 2,6-dichlorophenol, phenol, chlorobenzene, and benzene. In contrast to pyrolysis, 4,6-DCDF is the major product rather than DD, and 1-MCDD and naphthalene are formed at temperatures as low as 400 °C. Under oxidative conditions, ?OH and Cl? are the major carriers, which favors 4,6-DCDF formation over DD or 1-MCDD through abstraction of H? through diketo- and ether- intermediates. It is proposed that below 500 °C, unimolecular tautomerization/HCl elimination and CO elimination/isomerization reactions result in the formation of 1-MCDD and naphthalene, respectively.
- Evans, Catherine S.,Dellinger, Barry
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- A detailed mechanism of the surface-mediated formation of PCDD/F from the oxidation of 2-chlorophenol on a CuO/Silica surface
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The formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) via a Cu(II)O-mediated reaction of 2-chlorophenol (2-MCP) has been studied in a packed bed reactor over a temperature range of 200-500 °C. Under oxidative conditions, the principle PCDD/F products were 1-monochlorodibenzo-p-dioxin (MCDD) > 4,6-dichlorodibenzofuran (DCDF) > dibenzo-p-dioxin (DD). EPR studies indicated the presence of a carbon-centered phenoxyl radical on the surface, which is attributed to chemisorption of 2-MCP at a copper oxide site followed by electron transfer to Cu(II) to form Cu(I) and a phenoxyl radical. The presence of a surface bound phenoxyl radical and the formation of MCDD, DCDF, and DD, which were also observed as the principle products of the gas-phase oxidation of 2-MCP, strongly suggest a surface-mediated mechanism involving many of the same radical and molecular species involved in the gas-phase formation of PCDD/F from 2-MCP. Reaction orders of 0.5-1.0 were observed for MCDD and DD formation, indicating an Eley-Rideal formation mechanism. Negative reaction orders were observed for DCDF formation, indicating a Langmuir-Hinshelwood formation mechanism. No highly chlorinated PCDFs were observed, suggesting a mechanism in which DCDF is desorbed from the surface before it can undergo additional chlorination. Highly chlorinated PCDDs were observed, which were consistent with a mechanism in which DD remained adsorbed to the surface and underwent additional chlorination. Chloro-o-quinone and chlorocatechol, which are precursors to semiquinone radicals, were also observed products. A detailed reaction mechanism accounting for all reported products is proposed.
- Lomnicki, Slawomir,Dellinger, Barry
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- Experimental determination of the enthalpy of formation of dibenzo- p-dioxin
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The standard molar enthalpy of combustion of dibenzo-p-dioxin (DD) was measured at T = 298.15 K by static-bomb combustion calorimetry: ΔcHmo(cr) = -(5723.8 ± 1.4) kJ·mol-1. The standard molar enthalpy of sublimation of this compound was g measured by microcalorimetry: Δcrg Hmo = (91.45 ± 0.76) kJ·mol-1. These values were used to derive the standard molar enthalpies of formation of DD in the crystalline and gaseous states: ΔfHmo(cr) = -(141.6 ± 2.1) kJ·mol-1 and ΔfHmo(g) = -(50.1 ± 2.2) kJ·mol-1. The specially obtained sample of DD of high purity {mole fraction x = (0.9999±0.0001)} was used in all measurements.
- Pimenova,Melkhanova,Kolesov,Demyanov,Fedotov
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- Dechlorination of polychlorinated dibenzo-p-dioxins catalyzed by noble metal catalysts under mild conditions
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Dechlorination of polychlorinated dibenzo-p-dioxins such as 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD) and 1,2,6,7-tetrachlorodibenzo-p-dioxin (1,2,6,7-TCDD) was carried out in a solution of NaOH in 2-propanol in the presence of carbon-supported noble metal
- Ukisu, Yuji,Miyadera, Tatsuo
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- Polyheteroarylenes based on 2,3,7,8-tetraaminodibenzo-p-dioxin and aromatic polyfunctional carboxylic acids
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Polynaphthoylene benzimidazole and polybenzimidazole were obtained via polycondensation of 2,3,7,8-tetraaminodibenzo-p-dioxin with aromatic di- and tetracarboxylic acids in polyphosphoric acid. From a solution of polynaphthoylene benzimidazole in methanesulfonic acid a heat-resistant fiber with high tensile strength was obtained. Aromatic polybenzimidazoles are promising materials for producing membranes of medium-temperature fuel cells.
- Mognonov,Ayurova, O. Zh.,Il’ina,Khakhinov
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- Hydrogen bonding promoted simple and clean photo-induced reduction of C-X bond with isopropanol
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We herein report a simple and clean photo-induced metal-free reduction of C-X bond under an atmosphere of air at room temperature. Isopropanol is used as both the reducing reagent and solvent. Various functional groups (acids, esters, alcohols, anilines, phenols, indoles, pyridines, cyano and trifluoromethyl groups) and other heterocyclic compounds are tolerated. Different organic halides (including C-I, C-Br and C-Cl bonds) can be dehalogenated with moderate to excellent yields. Polyhalides are also reduced chemoselectively and efficiently. DFT calculation suggests a six-membered ring transition state via C-X H-O hydrogen bonding to decrease the activation energy.
- Cao, Dawei,Yan, Chaoxian,Zhou, Panpan,Zeng, Huiying,Li, Chao-Jun
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p. 767 - 770
(2019/01/21)
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- Hydrodehalogenation of Polyhalogenated Aromatics Catalyzed by NiPd Nanoparticles Supported on Nitrogen-Doped Graphene
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Ni30Pd70 nanoparticles supported on nitrogen-doped graphene (NG) acts as a catalyst for the hydrodehalogenation of halogenated aromatics under mild reaction conditions. It reduces mono- or dichloroarenes to the corresponding dehalogenated arenes in >90 % yield in 10 % aqueous isopropanol solvent at or below 50 °C within 5 h. Tests on a variety of substrates containing various functional groups show that the catalyst is selective for reduction of C?Cl and C?Br bonds. In addition, this catalyst completely hydrodehalogenates high-concentration solutions of dioxin, polychlorinated biphenyls, chloroaromatic constituents of the defoliant agent orange, and polybrominated diphenyl ethers in 12 h. The catalyst is reusable and shows no morphological or compositional changes after 5 cycles. This methodology offers a powerful, low-cost, and safe technology for the degradation of polyhalogenated aromatics, and may be useful for preventing proliferation of these toxins in the environment from causing serious health issues.
- Guo, Xuefeng,Yu, Chao,Yin, Zhouyang,Sun, Shouheng,Seto, Christopher T.
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p. 1617 - 1620
(2018/06/15)
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- Highly active recyclable heterogeneous Pd/ZnO nanoparticle catalyst: Sustainable developments for the C-O and C-N bond cross-coupling reactions of aryl halides under ligand-free conditions
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Efficient Pd supported on ZnO nanoparticles for the ligand-free O-arylation and N-arylation of phenols and various N-H heterocycles with aryl chlorides, bromides, and iodides were readily synthesized and characterized. The amount of palladium on ZnO is 9.84 wt% (0.005 g of the catalyst contains 462 × 10-8 mol% of Pd) which was determined by ICP analysis. This nano sized Pd/ZnO with an average particle size of 20-25 nm and specific surface area 40.61 m2 g-1 was used as a new reusable heterogeneous catalyst for the formation of C-O and C-N bonds in organic synthesis. This protocol gives the arylated product in satisfactory yields without any N2 or Ar flow. The catalyst can be recovered and recycled several times without marked loss of activity.
- Hosseini-Sarvari, Mona,Razmi, Zahra
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p. 44105 - 44116
(2014/12/10)
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- HETEROCYCLIC COMPOUNDS AND METHODS FOR THEIR USE
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The present invention relates to heterocyclic compounds useful for antagonising angiotensin II Type 2 (AT2) receptor. More particularly the invention relates to piperidine compounds, compositions containing them and their use in methods of treating or preventing disorders or diseases associated with AT2 receptor function including neuropathic pain, inflammatory pain, conditions associated with neuronal hypersensitivity, impaired nerve conduction velocity, cell proliferation disorders, disorders associated with an imbalance between bone resorption and bone formation and disorders associated with aberrant nerve regeneration.
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Page/Page column 55
(2013/08/15)
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- SYNTHESIS OF CLAY-TEMPLATED SUBNANO-SIZED ZERO VALENT IRON (ZVI) PARTICLES, CLAYS CONTAINING SAME, AND USE OF BOTH IN CONTAMINANT TREATMENTS
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A clay comprising a 2:1 aluminosilicate clay having negative charge sites, the 2:1 aluminosilicate clay containing subnano-sized zero valent iron (ZVI) particles distributed on clay surfaces is provided. In one embodiment, at least some or all of the particles have a cross-section of five (5) angstroms or less. Methods of synthesizing and the novel clays and the clay-templated subnano-scale ZVI particles themselves are also described. Such novel products are useful in a variety of remediation applications, including for reduction and dechlorination reactions.
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Page/Page column 7-8
(2011/06/23)
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- Formation of chlorinated phenols, dibenzo-p-dioxins, dibenzofurans, benzenes, benzoquinnones and perchloroethylenes from phenols in oxidative and copper (II) chloride-catalyzed thermal process
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Formation of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and chlorinated phenols on CuCl2 from unsubstituted phenol and three monochlorophenols was studied in a flow reactor over a temperature range of 100-425 °C. Heated nitrogen gas streams containing 8.0% oxygen were used as carrier gas. The 0.00024 mol of unsubstituted phenol and 0.00039 mol of each monochlorophenol were passed through a 1 g and 1 cm SiO2 particle containing 0.5% (Cu by mass) CuCl2. Chlorination preferentially occurred on ortho-(2, 6) and para-(4) positions. Chlorination increased up to 200 °C, and thereafter decreased as temperature increased. Chlorination of phenols plays an important role in the formation of the more chlorinated PCDD/Fs. Chlorinated benzenes are formed possibly from both chlorination of benzene and chlorodehydroxylation of phenols. Chlorinated phenols with ortho chlorine formed PCDD products, and major PCDD products were produced via loss of one chlorine. For PCDF formation, at least one unchlorinated ortho carbon was required.
- Ryu, Jae-Yong
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p. 1100 - 1109
(2008/12/21)
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- Role of temperature and hydrochloric acid on the formation of chlorinated hydrocarbons and polycyclic aromatic hydrocarbons during combustion of paraffin powder, polymers, and newspaper
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Formation of chlorinated hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) were determined using a laboratory-scale incinerator when combusting materials at different temperatures, different concentrations of hydrochloric acid (HCl), and when combusting various types of polymers/newspaper. Polychlorobenzenes (PCBz), polychlorophenols (PCPhs), polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) and their toxic equivalency (TEQ) and PAHs were highlighted and reported. Our results imply maximum formation of chlorinated hydrocarbons at 400°C in the following order; PCBz≥PCPhs?PCDFs>PCDDs>TEQ on a parts-per-billion level. Similarly, a maximum concentration of chlorinated hydrocarbons was noticed with an HCl concentration at 1000 ppm with the presence of paraffin powder in the following order; PAHs>PCBz≥PCPhs?PCDFs>PCDDs>TEQ an a parts-per-billion level. PAHs were not measured at different temperatures. Elevated PAHs were noticed with different HCl concentrations and paraffin powder combustion (range: 27-32 μg/g). While, different polymers and newspaper combusted, nylon and acrylonitrile butadiene styrene (ABS) produced the maximum hydrogen cyanide (HCN) concentration, concentrations of PCDD/FS, dioxin-like polychlorinated biphenyls (DL-PCBs), and TEQ were in a decreasing order: polyvinylchloride (PVC)newspaperpolyethyleneterephthalate (PET) polyethylene (PE) polypropylene (PP) ABS = blank. Precursors of PCBs were in a decreasing order: PPnylonPEnewspaperABSPVCblankPET. Precursors of PCDD/Fs were in a decreasing order: newspaper PP= nylonPEABSPVC= blankPET. BTX formation was in a decreasing order; PEnylonnewspaperABSPP. PAHs formation were elevated with parts-per-million levels in the decreasing order of PPnylonPE newspaperblankABS PETPVC.
- Takasuga, Takumi,Umetsu, Norihito,Makino, Tetsuya,Tsubota, Katsuya,Sajwan, Kenneth S.,Kumar, Kurunthachalam Senthil
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- Photochemical rearrangement of chlorinated dibenzo-p-dioxins. Regioselective carbon-oxygen bond homolysis from the singlet excited state, and carbon-chlorine bond homolysis from the triplet excited state
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UV light irradiation of 1-chloro-, 2-chloro-, 1,2-dichloro-, 2,3-dichloro-, and 2,7-dichlorodibenzo-p-dioxin in methanol leads to regioselective homolysis of carbon-oxygen bond from the singlet excited state to undergo rearrangement into chlorinated 2,2′-biphenols. On the contrary, reaction from the triplet excited state of chlorinated dioxins results in selective formation of dechlorinated congeners without altering the dioxin skeleton. Copyright
- Kobayashi, Takanori,Shimada, Jun-Ichi,Kitahara, Chieko,Haga, Naoki
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p. 348 - 349
(2007/10/03)
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- Mechanisms of dioxin formation from the high-temperature oxidation of 2-bromophenol
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The homogeneous, gas-phase oxidative thermal degradation of 2-bromophenol was studied in a 1 cm i.d., fused silica flow reactor at a concentration of 88 ppm, reaction time of 2.0 s, over a temperature range from 300 to 1000 °C. Observed products in order of yield were dibenzo-p-dioxin (DD) > 4,6-dibromodibenzofuran (4,6-DBDF) > 4-monobromodibenzofuran (4-MCDF), dibenzofuran (DF), 1-monobromodibenzo-p-dioxin (1-MBDD), naphthalene, bromonaphthalene, 2,4-dibromophenol, 2,6-dibromophenol, phenol, bromobenzene, and benzene. This result is in contrast to the oxidation of 2-chlorophenol, where the major product is 4,6-dichlorodibenzofuran (4,6-DCDF). 4,6-DBDF was observed in high yields in contrast to our previous results for the pyrolysis of 2-bromophenol, where 4,6-DBDF was not detected. The increase in 4,6-DBDF yields is attributed to hydroxyl radical being the major chain carrier under oxidative conditions, which favors hydrogen-abstraction reactions that lead to formation of 4,6-DBDF. However, DD is still the highest yield product under oxidative conditions because of the relative ease of displacement of Br? in the ring-closure reaction.
- Evans, Catherine S.,Dellinger, Barry
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p. 2128 - 2134
(2007/10/03)
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- Mechanisms of Dioxin Formation from the High-Temperature Pyrolysis of 2-Bromophenol
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Brominated hydrocarbons are the most commonly used flame retardants. Materials containing brominated hydrocarbons are frequently disposed in municipal and hazardous waste incinerators as well as being subjected to thermal reaction in accidental fires. This results in the potential for formation of brominated dioxins and other hazardous combustion byproducts. In contrastto chlorinated hydrocarbons, the reactions of brominated hydrocarbons have been studied only minimally. As a model brominated hydrocarbon that may form brominated dioxins, we studied the homogeneous, gas-phase pyrolytic thermal degradation of 2-bromophenol in a 1-cm i.d., fused-silica flow reactor at a concentration of 90 ppm, with a reaction time of 2.0 s, and over a temperature range of 300 to 1000 °C. Observed products included dibenzo-p-dioxin (DD), 1-monobromodibenzo-p-dioxin (I-MBDD), 4-monobromodibenzofuran (4-MBDF), dibenzofuran (DF), naphthalene, bromonaphthalene, 2,4- and 2,6-dibromophenol, phenol, bromobenzene, and benzene. These results are compared and contrasted with previous results reported for 2-chlorophenol. At temperatures lower than 700 °C, formation of 2-bromophenoxyl radical, which decomposes through CO elimination to form a bromocyclopentadienyl radical, forms naphthalene and 2-bromonaphthalene through radical recombination/rearrangement reactions. However, unlike the results for 2-chlorophenol, where naphthalene is the major product, DD becomes the major product for the pyrolysis of 2-bromophenol. The formation of DD and 1-MBDD are attributed to radical-radical reactions involving 2-bromophenoxyl radical with the carbon- (bromine) centered radical and the carbon- (hydrogen) centered radical mesomers of 2-bromophenoxyl radical, respectively. The potential product, 4,6-dibromodibenzofuran (4,6-DBDF) for which the analogous product, 4,6-dichlorodibenzofuran (4,6 DCDF), was observed in the oxidation of 2-chlorophenol, was not detected. This is attributed to the pyrolytic conditions of our experiments (e.g., shorter reaction times and higher temperatures) that favor reaction intermediates that form DD and 1-MBDD.
- Evans, Catherine S.,Dellinger, Barry
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p. 5574 - 5580
(2007/10/03)
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- Electrocarboxylation of chlorinated aromatic compounds
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Chorinated benzenes (1, 4), biphenyls (6, 9), dibenzofurans (10, 15, 17, 18), 2-chlorodibenzo[1,4]dioxine (24) and 1-chloronaphthalene (26) as well as dibenzofuran (12) and naphthalene (27) themselves were transformed into carboxylic acids by galvanostatic electroreduction in the presence of carbon dioxide ("electrocarboxylation"). Dry DMF was used as solvent, zinc or stainless steel as cathode and magnesium as a sacrificial anode in an undivided cell. Hydrogenation of aromatic rings was not observed. However, reductive addition of two molecules of carbon dioxide to form dihydrodicarboxylic acids, e.g. 22 and 29, occurs in the dibenzofuran and naphthalene series.
- Golinske, Dirk,Voss, Juergen,Adiwidjaja, Gunadi
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p. 862 - 880
(2007/10/03)
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- Influence of combustion conditions on the PCDD/F-, PCB-, PCBz- and PAH- concentrations in the post-combustion chamber of a waste incineration pilot plant
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Experiments at a pilot scale waste incinerator (0.5 MW thermal power) showed that the conditions in the postcombustion chamber (650-900°C) are strongly influencing the formation of chlorinated and non-chlorinated aromatics. Non-optimal combustion conditions resulted in increased concentrations of mono- to trichlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and polycyclic aromatic hydrocarbons (PAH), while chlorinated benzenes (PCBz), polychlorinated biphenyls (PCB) and the higher chlorinated PCDD/F are only weakly affected or even decrease. The changes in concentration of the compounds investigated over a time span of hours gave hints on 'memory effects' in this combustion zone. For mono- and dichlorinated benzenes, a high correlation (r2 = 0.80) with the international toxicity equivalent (I-TEQ) value of PCDD/F was observed. As recently has been demonstrated, this correlation can be utilized for an indirect on-line measurement of the I-TEQ by a novel laser mass spectrometric technique (REMPI-TOFMS). (C) 2000 Elsevier Science Ltd.
- Blumenstock,Zimmermann,Schramm,Kettrup
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p. 987 - 993
(2007/10/03)
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- Influence of variation in combustion conditions on the primary formation of chlorinated organic micropollutants during municipal solid waste combustion
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The aim of this study was to investigate the influence of variation in combustion conditions on the primary formation of organic micropollutants (OMPs). The flue gas samples were taken at a relatively high flue gas temperature (650°C), to enable mechanistic studies on the high temperature formation (primary formation). Eleven experiments were performed in a laboratory scale fluidized bed reactor fed with an artificial municipal solid waste (MSW). The samples were analyzed for mono- to octachlorinated dibenzo- p-dioxins and dibenzofurans (CDDs/Fs), tri- to decachlorinated biphenyls (CBs), di- to hexachlorinated benzenes (CBzs), and di- to pentachlorinated phenols (CPhs). In addition to chlorinated OMPs, nonchlorinated dibenzo-p- dioxin (DD), dibenzofuran (DF), and biphenyl (BP) were analyzed. The experiments show that variations in the CE influence the degree of chlorination of the organic micropollutants. A correlation between low CE and formation of non- and low-chlorinated DMPs was seen and a distinct relationship of higher chlorinated homologues and efficient combustion condition. Thus, the DiCDFs and DiCBzs are formed during low combustion efficiency (CE), while the PeCDF and PeCBzs formation take place at higher CE. The distribution between primary and secondary air is important for the formation of higher CDD/Fs and CBzs. The primary formation of CDDs and CDFs is through different mechanisms. The CDDs are mainly formed by condensation of CPhs, while the CDFs are formed through a non- or a low-chlorinated precursor followed by further chlorination reactions.
- Wikstroem,Tysklind,Marklund
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p. 4263 - 4269
(2007/10/03)
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- Towards the synthesis of aminodibenzo[b,e][1,4]dioxin derivatives via cationic ruthenium complexes
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Double nucleophilic aromatic substitution reactions between N-substituted (η6-1,2-dichlorobenzene)RuCp+ salts and substituted 1,2-benzenediols have been carried out under mild conditions to prepare N-substituted (η6-dibenzo[b,e][1,4]dioxin)ruthenium(II) complexes. The dibenzodioxin ligands were subsequently liberated by photolysis, with radiation from a sunlamp or from a medium pressure Hg lamp (300 nm).
- Cambie, Richard C.,Clark, George R.,Coombe, Sheryl L.,Coulson, Sally A.,Rutledge, Peter S.,Woodgate, Paul D.
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- Preparative supercritical deuterium exchange in arenes and heteroarenes
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Deuterated homo- and heterocyclic aromatic substrates bearing various functionalities were prepared by isotope exchange in supercritical deuterium oxide, with little or no formation of byproducts. Equilibration was attained rapidly (1-24 hrs), and deuterium exchange extended to alpha positions of alkyl homologs. Nitro- and haloarenes, thioethers, telluroethers, and some heterocyclic substrates were unstable.
- Junk, Thomas,Catallo, W. James
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p. 3445 - 3448
(2007/10/03)
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- Syntheses of dibenzodioxin derivatives via iron complexes, and further functionalizations via directed metallation
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Double nucleophilic aromatic substitution reactions between (cyclopentadienyl)(η6-1,2-dichlorobenzene)iron(1 +) salts and substituted 1,2-benzenediols have been carried out under mild conditions to prepare 6-dibenzodioxin>iron(1 +) complexes functionalized in the 1- or 2-position with an alkyl, aldehyde, carboxylic acid, methoxycarbonyl, carboxamide, or hydroxy group. 3-Methyl- and 4-methyl-(η6-1,2-dichlorobenzene)iron complexes were treated with substituted 1,2-benzenediols to effect functionalization of both aromatic rings of the heterocycle.The dibenzodioxin ligands were liberated routinely by irradiation with ultraviolet light.Directed deprotonation of the free functionalized dibenzodioxins with an alkyllithium reagent followed by quenching with a variety of electrophiles yielded further derivatives, including two new isoindolone systems.
- Cambie, Richard C.,Janssen, Sally J.,Rutledge, Peter S.,Woodgate, Paul D.
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p. 387 - 418
(2007/10/02)
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- An Improved Synthesis of Substituted Dibenzodioxines
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An improved general synthesis of substituted dibenzodioxines by reaction of catechol and substituted 1,2-dichloro- or 2-chloronitro-benzenes with metallic potassium in hexamethylphosphoramide is reported.The yields are generally superior to those in published methods, and in particular the reaction appears the one of choice for the synthesis of both the parent dibenzodioxine and the 1-carboxy derivative.
- Lee, Ho H.,Denny, William A.
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p. 1071 - 1074
(2007/10/02)
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- ARENE COMPLEXES OF TRANSITION METALS IN REACTIONS WITH NUCLEOPHILIC REAGENTS. XI. SYNTHESIS OF HETEROCYCLIC COMPOUNDS BY NUCLEOPHILIC SUBSTITUTION OF CHLORINE ATOMS IN η6-o-DICHLOROBENZENECHROMIUM TRICARBONYL
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A method was developed for the synthesis of dibenzo-1,4-dioxin, phenoxazine, and phenoxathiin and also their chromium tricarbonyl complexes by the reaction of η6-o-dichlorobenzenechromium tricarbonyl with the alkali-metal salts of pyrocatechol, o-aminophenol, and o-mercaptophenol in HMPTA.The composition of the reaction products and the yield of the heterocyclic compounds depend significantly on the nature of the solvent, the nucleophile, the condensing agent, and the reaction conditions.
- Litvak, V. V.,Goryunov, L. I.,Shteingarts, V. D.
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p. 138 - 144
(2007/10/02)
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- IMPROVED ULLMANN SYNTHESIS OF DIARYL ETHERS
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Several diaryl ethers have been synthesized by using indefinitely stable and easily available copper(I) phenylacetylenide as condensing agent in Ullmann condensation reaction.
- Afzali, A.,Firouzabadi, H.,Khalafi-nejad, A.
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p. 335 - 340
(2007/10/02)
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- ELECTRON TRANSFER AS ELEMENTARY STAGE IN ELECTROPHILIC NITRATION OF DIBENZO-p-DIOXIN
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The formation of the radical-cation of dibenzo-p-dioxin in the reaction of dibenzo-p-dioxin with nitrating agents was recorded by the ESR method and electronic spectroscopy.Photometric investigation of the reaction of this compound with nitric acid in trifluoroacetic acid showed that the nature and composition of the products depend on the molar ratio of nitric acid and the substrate.With a deficiency of nitric acid the radical-cation or its mixture with the dinitro derivatives of dibenzo-p-dioxin are formed, whereas with an excess of nitric acid only a mixture of the dinitro compounds is formed.Analysis of these facts led to the conclusion that the nitration of dibenzo-p-dioxin with nitric acid in trifluoroacetic acid includes the stage of one-electron oxidation of the initial aromatic compound.
- Morkovnik, A. S.,Belinskii, E. Yu.,Dobaeva, N. M.,Okhlobystin, O. Ya.
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p. 328 - 335
(2007/10/02)
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- Synthesis and Some Heterocyclic Systems from Nucleophilic Substitution Reactions with η6-o-Dichlorobenzene-η5-cyclopentadienyliron Hexafluorophosphate
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A method for the synthesis of heterocyclic systems related to 9,10-dihydroanthracene with two hetero-atoms at the 9,10-positions is described.It involves the nucleophilic substitution reaction of η6-o-dichlorobenzene-η5-cyclopentadienyliron hexafluorophosphate with two nucleophilic groups (OH, SH and/or NH2) located in the 1,2-positions of a benzene ring to give a cyclopentadienyliron complexed heterocycle.Upon pyrolytic sublimation of the complex, the free heterocyclic compound is then obtained.
- Sutherland, Ronald G.,Piorko, Adam,Gill, Udai S.,Lee, Choi Chuck
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p. 801 - 803
(2007/10/02)
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- The Smiles Rearrangement of 2-Aryloxy-5-nitrophenoxides. Attempted Routes to Benzoxirens and Tribenzotrioxonins
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Formation of dibenzo-p-dioxins by the pyrolysis of 2-halogenophenoxides does not appear to involve intermediate benzoxirens.Thermal self-condensation to potassium 2-bromo-5-nitrophenoxide (1b) gave a mixture of 2,7- and 2,8-dinitrobenzo-p-dioxins (6d) and (6e).The mechanism of formation of the 2,8-isomer (6e) is shown to involve Smiles rearrangement of potassium 2-(2-bromo-5-nitrophenoxy)-5-nitrophenoxide (9a).Further examples of Smiles rearrangements of 2-aryloxy-5-nitrophenoxides and an attempted synthesis of the tribenzotrioxonin derivatives (16) are described.
- Ramsden, Christopher A.
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p. 2456 - 2463
(2007/10/02)
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