262-12-4Relevant articles and documents
Copper/iron-catalyzed Ullmann coupling of diiodo- and dibromoarenes and diphenols for the synthesis of aryl ether macrocycles
Zhou, Qizhong,Su, Liangjun,Jiang, Tiansheng,Zhang, Bin,Chen, Rener,Jiang, Huajiang,Ye, Yuyuan,Zhu, Mengqing,Han, Deman,Shen, Jianfen,Dai, Guoliang,Li, Zhanting
, p. 1125 - 1132 (2014)
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.
RADIOLYSIS OF POLYCHLORODIBENZODIOXINS IN HEXANE
Mitroshkov, A. V.,Revel'skii, I. A.,Podsoblyaev, A. P.,Egorov, V. V.,Kostyanovskii, R. G.
, p. 688 - 691 (1991)
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.
Mechanisms of dioxin formation from the high-temperature oxidation of 2-chlorophenol
Evans, Catherine S.,Dellinger, Barry
, p. 122 - 127 (2005)
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.
A detailed mechanism of the surface-mediated formation of PCDD/F from the oxidation of 2-chlorophenol on a CuO/Silica surface
Lomnicki, Slawomir,Dellinger, Barry
, p. 4387 - 4395 (2003)
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.
Experimental determination of the enthalpy of formation of dibenzo- p-dioxin
Pimenova,Melkhanova,Kolesov,Demyanov,Fedotov
, p. 385 - 390 (2002)
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.
Dechlorination of polychlorinated dibenzo-p-dioxins catalyzed by noble metal catalysts under mild conditions
Ukisu, Yuji,Miyadera, Tatsuo
, p. 507 - 510 (2002)
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
Polyheteroarylenes based on 2,3,7,8-tetraaminodibenzo-p-dioxin and aromatic polyfunctional carboxylic acids
Mognonov,Ayurova, O. Zh.,Il’ina,Khakhinov
, p. 1903 - 1907 (2018)
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.
Hydrogen bonding promoted simple and clean photo-induced reduction of C-X bond with isopropanol
Cao, Dawei,Yan, Chaoxian,Zhou, Panpan,Zeng, Huiying,Li, Chao-Jun
, p. 767 - 770 (2019/01/21)
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.
Hydrodehalogenation of Polyhalogenated Aromatics Catalyzed by NiPd Nanoparticles Supported on Nitrogen-Doped Graphene
Guo, Xuefeng,Yu, Chao,Yin, Zhouyang,Sun, Shouheng,Seto, Christopher T.
, p. 1617 - 1620 (2018/06/15)
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.
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
Hosseini-Sarvari, Mona,Razmi, Zahra
, p. 44105 - 44116 (2014/12/10)
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.
