- Photoisomerisation of bicyclo[4.2.0]octadienes to tricyclo[4.2.0.02,5] octenes: Application to the synthesis of [n]ladderanes
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A new approach for the extension of [n]ladderanes is described which involves formation of an end-fused bicyclo[4.2.0]octadiene and its photoisomerisation to the related tricyclo[4.2.0.02,5] octene as the ladderane extension step. The protocol is illustrated with the synthesis of [3]ladderane (9) from an unsubstituted cyclobutene and nor[5]ladderane (13) from an ester activated cyclobutene. The exo-stereochemistry of (13) is confirmed by reference to intermediate (23) for which a single crystal X-Ray structure analysis was obtained.
- Warrener,Pitt,Nunn,Kennard
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- Photochemistry of Polyhaloarenes. 7. Photodechlorination of Pentachlorobenzene in the Presence of Sodium Borohydride
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The mechanism of photodechlorination of pentachlorobenzene (1) in acetonitrile has been examined.The quantum yield of reaction (Φr) has been found to vary with the concentration of 1.A charge-transfer intermediate formed from the triplet excited state of 1 is proposed to explain the observations. Φr increases with added NaBH4 and 1/Φr varies directly with the inverse of the concentration of the electron-transfer reagent.The regiochemistry deuterium isotope effects, tracer studies, and quenching analyses are consistent with an electron-transfer process.
- Freeman, Peter K.,Ramnath, N.
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- Preparation method for 3,5,-dichloro-2,4,-difluoroaniline
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The invention relates to the field of organic synthesis, specifically to a preparation method for 3,5,-dichloro-2,4,-difluoroaniline and application thereof. The preparation method for 3,5,-dichloro-2,4,-difluoroaniline provided by the invention comprises the following steps: 1) nitration reaction; 2) reduction reaction; 3) diazotization reaction; 4) nitration reaction; 5) fluorination reaction; and 6) reduction reaction. The preparation method for 3,5,-dichloro-2,4,-difluoroaniline provided by the invention has the following beneficial effects: 1) the method has mild reaction conditions, is stable and controllable, has less active sites, is insusceptible to side reaction, and has good yield and quality in the whole line; and 2) raw materials are cheap and easily available, so cost can be effectively reduced, and energy is saved; meanwhile, the use of chlorine gas is avoided, so the method is environment-friendly.
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- Formation and destruction of chlorinated pollutants during sewage sludge incineration
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The limitations facing land filling and recycling and the planned ban on sea disposal of sludge leads to the expectation that the role of sludge incineration will increase in the future. The expected increase in sludge incineration will also increase scrutiny of the main drawback to sewage sludge incineration-the formation of hazardous air pollutants (HAPs). Despite the extensive body of knowledge available on sewage sludge combustion, very few studies have been conducted on the formation of HAPs during sludge combustion. In this work, the interactions between sewage sludge pyrolysis products and sludge ash were investigated using a dual chamber flow reactor system and a horizontal laboratory scale reactor. The results of this study shows that sludge ash can catalyze oxidation and chlorination of organics. In the absence of HCl in the gas stream, sludge ash acts as an oxidizing catalyst, but in the presence of HCl, sludge ash acts as a chlorination catalyst producing high yields of organochloride compounds.
- Fullana, Andres,Conesa, Juan A.,Font, Rafael,Sidhu, Sukh
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p. 2953 - 2958
(2007/10/03)
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- Reactions of 2,4,6-trichlorophenol on model fly ash: Oxidation to CO and CO2, condensation to PCDD/F and conversion into related compounds
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Thermal treatment of 2,4,6-trichlorophenol on a magnesium silicate-based model fly ash in the temperature range between 250°C and 400°C leads predominantly to carbon monoxide and carbon dioxide. The fraction of 2,4,6-trichlorophenol which is oxidized to CO and CO2 increases from 3% at 250°C to 75% at 400°C. Further products are polychlorinated benzenes, dibenzo-p-dioxins, dibenzofurans and phenols. The homologue and isomer patterns of the chlorobenzenes suggest chlorination in the ipso-position of the trichlorophenol. The formation of PCDD from 2,4,6-trichlorophenol and 2,3,4,6-tetrachlorophenol on municipal solid waste incinerator fly ashes and model fly ash were compared and the reaction order calculated.
- Hell,Stieglitz,Altwicker,Addink,Will
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p. 697 - 702
(2007/10/03)
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- Identification of surrogate compounds for the emission of PCDD/F (I-TEQ value) and evaluation of their on-line realtime detectability in flue gases of waste incineration plants by REMPI-TOFMS mass spectrometry
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Correlations between products of incomplete combustion (PIC), e.g., chloroaromatic compounds, can be used to characterise the emissions from combustion processes, like municipal or hazardous waste incineration. A possible application of such relationships may be the on-line real-time monitoring of a characteristic surrogate, e.g., with Resonance-Enhanced Multiphoton Ionization-Time-of-Flight Mass Spectrometry (REMPI-TOFMS). In this paper, we report the relationships of homologues and individual congeners of chlorinated benzenes (PCBz), dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and phenols (PCPh) to the International Toxicity Equivalent (I-TEQ) of the PCDD/F (I-TEQ value) in the flue gas and stack gas of a 22 MW hazardous waste incinerator (HWI). As the REMPI detection sensitivity is decreasing with the increase of the degree of chlorination, this study focuses on the lower chlorinated species of the compounds mentioned above. Lower chlorinated species, e.g., chlorobenzene (MCBz), 1,4-dichlorobenzene, 2,4,6-trichlorodibenzofuran or 2,4-dichlorophenol, were identified as I-TEQ surrogates in the flue gas. In contrast to the higher chlorinated phenols, the lower chlorinated phenols (degree of chlorination 4) were not reliable as surrogates in the stack gas. The identified surrogates are evaluated in terms of their detectability by REMPI-TOFMS laser mass spectrometry. The outcome is that MCBz is the best suited surrogate for (indirect) on-line measuring of the I-TEQ value in the flue gas by REMPI-TOFMS. The correlation coefficient r of the MCBz concentration to the I-TEQ in the flue gas was 0.85.
- Blumenstock,Zimmermann,Schramm,Kettrup
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p. 507 - 518
(2007/10/03)
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- Radiation induced catalytic dechlorination of hexachlorobenzene on oxide surfaces
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Radiation induced catalytic dehalogenation of hexachlorobenzene (HCB) adsorbed to alumina (Al2O3), silica (SiO2), titania (TiO2), zirconia (ZrO2), and a commercially available zeolite has been studied using Cobalt-60 (60Co) as a radiation source. Solid-particulate samples were irradiated over a dose range of 0-58 kGy, and the chemical changes were monitored using Fourier transform infrared diffuse reflectance (FTIR-DR) and gas chromatography with electron capture detection (GC-ECD). The extent of HCB degradation on the metal oxides was found to increase dramatically in samples evacuated under vacuum, pointing to the competitive scavenging of conduction band electrons by surface adsorbed species, primarily oxygen. Coadsorbed water diminished HCB conversion on all oxides but to a greater degree on alumina. HCB degradation on metal oxides was found to be highly dependent upon the conduction band energy of the support material, thus confirming the occurrence of ultra-band-gap excitation and charge separation in irradiated oxides. Higher yields of dechlorination products were witnessed in alumina and silica samples. Zeolite, titania, and zirconia were also found to be inefficient in promoting radiation induced catalysis. The absence of oxidation products in the irradiated HCB/oxide samples suggests the inaccessibility of holes to undergo interfacial charge transfer with the organic substrate.
- Zacheis, George Adam,Gray, Kimberly A.,Kamat, Prashant V.
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p. 4715 - 4720
(2007/10/03)
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- Radiolytic reduction of hexachlorobenzene in surfactant solutions: A steady-state and pulse radiolysis study
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Steady-state and pulse radiolysis experiments have been performed to gain insight into the mechanism of hexachlorobenzene (HCB) degradation in nonionic surfactant (Plurafac RA-40) solutions. This understanding is important for the environmental application of radiolysis to remediate soils contaminated with chlorinated aromatic compounds or to treat surfactant solution wastes from soil washing processes. Steady-state experiments showed that, after an applied dose of 50 kGy, reductive dechlorination of HCB to trichlorobenzene occurs under reducing conditions. Under oxidizing conditions at the same dose, reductive dechlorination proceeds more slowly to yield tetrachlorobenzene. Radiolytic experiments on the surfactant alone showed that the reaction rate constant between hydroxyl radicals and RA-40 (1.09 x 109 M-1 s-1) was nearly 2 orders of magnitude higher than that between hydrated electrons and RA-40 (2.0 x 107 M-1 s-1). Reaction kinetics analysis indicates efficient hydroxyl radical scavenging by surfactant molecules and the production of secondary surfactant radicals, which are reductive in nature. Thus, we observe HCB dechlorination in surfactant solutions even under strongly oxidizing conditions. Steady-state and pulse radiolysis experiments have been performed to gain insight into the mechanism of hexachlorobenzene (HCB) degradation in nonionic surfactant (Plurafac RA-40) solutions. This understanding is important for the environmental application of radiolysis to remediate soils contaminated with chlorinated aromatic compounds or to treat surfactant solution wastes from soil washing processes. Steady-state experiments showed that, after an applied dose of 50 kGy, reductive dechlorination of HCB to trichlorobenzene occurs under reducing conditions. Under oxidizing conditions at the same dose, reductive dechlorination proceeds more slowly to yield tetrachlorobenzene. Radiolytic experiments on the surfactant alone showed that the reaction rate constant between hydroxyl radicals and RA-40 (1.09 × 109 M-1 s-1) was nearly 2 orders of magnitude higher than that between hydrated electrons and RA-40 (2.0 × 107 M-1 s-1). Reaction kinetics analysis indicates efficient hydroxyl radical scavenging by surfactant molecules and the production of secondary surfactant radicals, which are reductive in nature. Thus, we observe HCB dechlorination in surfactant solutions even under strongly oxidizing conditions.
- Zacheis,Gray,Kamat
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p. 3401 - 3407
(2007/10/03)
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- Pyrolysis of tricyclic cyclobutane-fused sulfolanes as a route to cis-1,2-divinyl compounds and their Cope-derived products
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Functionalisation of the double bond of 3-thiabicyclohept-6-ene 3, readily formed by hydrolysis of the cycloadduct 1 of 3-sulfolene and maleic anhydride followed by oxidative bis-decarboxylation, gives tricyclic sulfones 5-7 and 9 with the bicyclo2,4> skeleton. FVP of 3 results in stereospecific extrusion of SO2 to give Z-hexa-1,3,5-triene which undergoes electrocylisation to give cyclohexa-1,3-diene while reaction of 3 with LiAlH4 results in non-stereospecific extrusion to give Z- and E-hexa-1,3,5-triene. Upon FVP the tricyclic sulfones 5-7 and 9 lose SO2 to give 7-membered ring products 16-19 by Cope rearrangement of the initially formed cis-1,2-divinyl intermediates 15. The 1,3-dipolar cycloaddition of nitrile oxides and a nitrone to the double bond of 3 gives tricyclic sulfones with the tricyclo2,6> skeleton and a wider variety of these can be prepared by conventional reactions of 1. Upon FVP these lose SO2 to give stable cis-1,2-divinyl compounds 23, 24, 37-40 and 41-44. The Diels-Alder adducts 48 and 49 have been prepared from 3 and these behave differently upon FVP, losing SO2 and butadiene to give tetrasubstituted benzenes, in the latter case by way of an unexpected tetracyclic intermediate.
- Aitken, R. Alan,Cadogan, J. I. G.,Gosney, Ian,Humphries, Caroline M.,McLaughlin, Leo M.,Wyse, Stuart J.
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p. 605 - 614
(2007/10/03)
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- Catalytic Dehalogenation of Highly Chlorinated Benzenes and Aroclors Using PdCl2(dppf) and NaBH4: Efficiency, Selectivity, and Base Support
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Reported herein is a convenient one-pot system that can dehalogenate highly chlorinated benzenes at room temperature with reasonable conversion rates using PdCl2(dppf) (dppf = 1,1′-bis-(diphenylphosphino)ferrocene) as catalyst, NaBH4 as reducing agent, TMEDA (N,N,N',N'-tetra-methyl-1,2-ethylenediamine) as supporting base, and THF as solvent. Total conversion of substrate to less chlorinated isomers is achieved within 200 h when hexachloro-, pentachloro-, and tetrachlorobenzenes are used. Degradation to benzene is not achievable, but the efficiency shown in the partial dechlorination is encouraging. A pronounced selectivity is accomplished with removal of meta-substituted chlorines being preferred over ortho- or para-substituted Cl atoms. The sequence in which reagents are added is also critical, thus indicating a protective role of the base. The effectiveness of the method was tested on the PCB mixtures Aroclor 1242, 1248, and 1254. Dechlorination efficiency at 67 °C is satisfactory.
- Lassová, Luisa,Lee, Hian Kee,Hor, T.S. Andy
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p. 3538 - 3543
(2007/10/03)
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- Methanesulfonylation of deactivated aromatics with superelectrophilic CH3so2F·3SbF5 and (CH3so2)2O-2CF3so 3H/B(O3SCF3)3 systems
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Methanesulfonylation of various deactivated arenes, including tri- and tetrafluorobenzenes, was achieved in good yield under mild conditions using superelectrophilic CH3SO2F/3SbF5 and (CH3SO2O)2O/2CF3SO 3H-B(O3SCF3)3 reagent systems. 1998 MAHK "Hayka/Interperiodica".
- Olah,Orlinkov,Oxyzoglou,Prakash, G.K. Suria
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p. 1573 - 1578
(2007/10/03)
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- Photoinduced Charge Separation in Rigid Bichromophoric Compounds and Charge Transfer State Electron Transfer Reactivity
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Bichromophoric compounds giving, after photoexcitation, a locally excited state (LE) rapidly followed by an intramolecular charge transfer (CT) state were designed using a Paddon-Row type synthesis.The electron-accepting end of the CT state is chosen in order to play the role of an electron relay versus external acceptors.In this way, electron transfer photosensitization is made available by using the CT state of bichromophores.The photophysics of the synthesized bichromophores is discussed, and the reductive dechlorination of polychlorinated benzenes is used as a test reaction.The bichromophoric sensitizer is unexpectedly found to be totally regenerated: the reaction is shown to be initiated by an electron transfer from the CT state to the chlorinated quencher.A rapidly breaking radical anion leads to the dechlorination, while the recombination of the sensitizer radical cation with the released chloride anion opens the way to the sensitizer recovery.
- Jiwan, J. L. Habib,Soumillion, J. Ph.
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p. 14223 - 14230
(2007/10/02)
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- Photodechlorination of polychlorobenzene congeners in surfactant micelle solutions
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Photochemical reactions of polychlorobenzene congeners in aqueous solutions containing surfactant micelles have been investigated. Photoreduction through photodechlorination was shown to be the main decay pathway in which lesser chlorinated congeners and benzene were formed as intermediates. Final products included H+ and Cl- in approximately stoichiometric amounts. Several hydrogen sources were investigated with sodium borohyride shown to be a promising rate enhancer at elevated concentrations. -Authors
- Wei Chu,Jafvert
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p. 2415 - 2422
(2007/10/03)
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- Sequential Cycloaddition-Cycloreversion-Cycloaddition-Cope Rearrangement with an Annelated Norbornadiene and Electrophlic Dienes. Unusual 2s + ?2a + ?2a>Transformation of a Pentacyclo-7,10.04,13.06,11>octadeca-3,8,14,17-tetraene.
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Hexachloronorbornadiene efficiently forms a 1:1 adduct 3 with 5,6-bismethylenenorbornene.Adduct 3 on reaction with 1,2,3,4-tetrachlorothiophene dioxide (TCTD) under mild conditions gives an SO2 bridged adduct,which loses SO2, the product cycloreverting to give 1,2,3,4-tetrachlorobenzene and an annelated cyclopentadiene 8; 8 reacts further with TCTD to give, in 1:1 ratio, two compounds (14 and 15) shown by mass, 13C and 1H NMR spectroscopy and single crystal X-ray structure determination to be the stereoisomeric products of a rare type of specific diene capture by TCTD.E vidence is presented that this result (and analogous examples) is best understood in terms of ''normal'' ? cycloadditions to 8 as dienophile towards electron-deficient TCTD, followed by rapid Cope rearrangement of the SO2-bridged intermediate adducts to give the observed products.At low temperatures adduct 3 behaves as expected towards electron-deficient diene tetracyclone; the ? cycloadduct decarbonylates on mild thermolysis, concomitant cycloreversion also giving diene 8.At much higher temperatures in the presence of excess tetracyclone, diene 8 likewise behaves as dienophile; the carbonyl-bridged major cycloadduct decarbonylates to give an intermediate which undergoes an unusual thermally-allowed 2s + ?2a + ?2a> 1,3-shift/cycloaddition, delivering a symmetrical cage-like structure 24, as indicated by mass and 13C and 1H NMR spectroscopy.
- Gravett, Edward C.,Howard, Judith A. K.,Mackenzie, Kenneth,Shi-Xiong, Liu,Karadakov, Peter B.
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p. 4699 - 4710
(2007/10/02)
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- Photochemistry of Polyhaloarenes. 12. The Photochemistry of Pentachlorobenzene in Micellar Media
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The dependence of the reciprocal of the quantum yield for the photohydrodechlorination of pentachlorobenzene (1) in aqueous 0.100 M hexadecyltrimethylammonium bromide (CTAB) solution upon the reciprocal of the microconcentration of 1 and upon the reciprocal of the probability for excited state 1 reacting with ground-state 1 provides a linear correlation at high microconcentrations of 1.The regiochemistry of the photohydrodechlorination process in CTAB favors formation of 1,2,4,5-tetrachlorobenzene to a significantly smaller extent than is observed in the analogous process in acetonitrile solution in the presence of triethylamine.The bromotetrachlorobenzene byproduct is formed in the photolysis in the following composition: 1-bromo-2,3,4,5-tetrachloro- (5) : 2-bromo-1,3,4,5-tetrachloro- (6) : 3-bromo-1,2,4,5-tetrachlorobenzene (7) = 9.7 : 66.7 : 23.3.In a trapping experiment carried out during an irradiation of 1 in CH3CN/ H2O (8:2) in the presence of excess KBr at 254 nm, bromotetrachlorobenzenes (5:6:7) were formed in a ratio of 11.3 : 66.8 : 21.9.These experiments are rationalized by proposing that product in these micellar photohydrodechlorination reactions is formed by fission of triplet-state 1 and a competing process which involves conversion of triplet-state 1 to triplet excimer which then undergoes fragmentation.
- Freeman, Peter K.,Lee, Youn-Sik
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p. 2846 - 2850
(2007/10/02)
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- Photolyses of Polychloro- and Polybromobenzenes. Novel Isomerization in Solvents Resisting against Hydrogen Abstraction
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Polychloro- and polybromobenzenes were photolyzed in acetonitrile and perfluorohexane.Photolyses of polychlorobenzenes in acetonitrile gave isomerized products in addition to dechlorinated products, which appeared exclusively in the photolyses in hexane and other solvents carrying hydrogen atoms active to hydrogen abstraction.The photolyses in perfluorohexane gave isomerized products to a lesser extent.The reaction in this solvent gave predominantly polyhalobiphenyls which are assumed to be produced through coupling.Without exception the isomerized products have the structure which can be expected to be formed via 1,3-migration of chlorine atom, though it is not sure at present whether it takes place actually.The isomerization was shown to proceed intramolecularly.Some evidence and theoretical rationalization in favor of the 1.3-chlorine migration mechanism are given.
- Hirota, Minoru,Nakada, Masahiro
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p. 2926 - 2933
(2007/10/02)
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- Photochemistry of Polyhaloarenes. 8. The Photodechlorination of Pentachlorobenzene
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Measurements of the intersystem crossing yield of pentachlorobenzene triplet, the quenching of photodechlorination of pentachlorobenzene with fumaronitrile, the dependence of the fluorescence lifetime, and the quantum yield of photodechlorination of pentachlorobenzene upon substrate concentration and the dependence of relative product concentration upon light intensity provide evidence for three pathways to product: direct fission of singlet and triplet and fragmentation of triplet excimer.
- Freeman, Peter K.,Ramnath, N.,Richardson, Alan D.
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p. 3643 - 3646
(2007/10/02)
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- Photo-Rearrangement of Polychlorobenzenes meta-Migration of Chlorine Atom
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Several polychlorobenzenes were irradiated by ultraviolet light (254 nm) in acetonitrile and the products were determined by gas chromatography.In addition to the abstraction of hydrogen atom from the solvent, photo-isomerization was shown to proceed giving isomeric polychlorobenzenes one of which chlorine atoms migrated to meta to the original position.The meta-rearrangement was rationalized by an MNDO calculation on o-chlorophenyl free radical.
- Morisaki, Kenji,Miura, Yasuki,Abe, Kazuhisa,Hirota, Minoru,Nakada, Masahiro
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p. 1589 - 1592
(2007/10/02)
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- Thiophene S,N-Ylides: A New Versatile Class of Sulphimides
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Tetrachlorothiophene reacts with methyl, ethyl, and phenyl azidoformates and with toluene-p-sulphonyl azide at 130-150 deg C to give stable thiophene S,N-ylides. 2,5-Dichloro and 2,5-dibromo-thiophene and tetrabromothiophene yield products derived by nitrene attack at the α-position.The S,N-ylides undergo ready photolysis to liberate the parent nitrene, and react with a wide variety of electron-rich dienophiles as 4?-components to give tetrachlorodihydrobenzenes with extrusion of a thionitroso compound.With dienes the ylides react either as 2?- or 4?-systems.Thus with anthracene a dihydrothiophene analogue of triptycene is generated efficiently aromatised and de-ylidated with zinc in methanol.With dimethyl acetylenedicarboxylate the ylides yield a thiazocine by a novel ring expansion.Oxidation of the ylide system with 3-chloroperbenzoic acid gives the corresponding ylide S-oxide.Tetrachlorothiophene also reacts efficiently with diazoalkanes under rhodium acetate catalysis to give thiophene S,C-ylides, which undergo cycloaddition with nucleophilic alkenes much more slowly than their nitrogen analogues.
- Meth-Cohn, Otto,Vuuren, Gerda van
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p. 233 - 244
(2007/10/02)
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- The Photochemistry of Polyhaloarenes. 5. Fragmentation Pathways in Polychlorobenzene Radical Anions
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Negative chemical ionization mass spectroscopy of polychlorobenzenes reveals that parent radical anion undergoes fission by two pathways--(a) cleavage to aryl radical plus Cl- (kCl-) and (b) fission to aryl carbanion plus chlorine atom (kCl*)--and that there is a Hammett relationship between log(kCl*/kCl-) and Σ?.The dependence of the reciprocal of the quantum yield for photochemical dechlorination of trichlorobenzenes through pentachlorobenzene upon the reciprocal of the concentration of the electron donor, triethylamine, was analyzed in order to establish the optimum concentration for radical anion formation.The regiochemistries for the photodechlorination of trichlorobenzenes through pentachlorobenzene in the presence of triethylamine, with and without acetophenone sensitizer, were determined and found to be very similar and quite different from those observed for the direct photolysis in the absence of triethylamine for the comparison cases of 1,2,3,5-tetrachloro- and pentachlorobenzene.The regiochemistry of the fragmentation of polychlorobenzene radical anion to aryl radical plus chloride ion is rationalized in terms of a bent transition state.
- Freeman, Peter K.,Srinivasa, Ramanujan,Campbell, J.-A.,Deinzer, Max L.
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p. 5531 - 5536
(2007/10/02)
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- Participation of Solvent Dimethylformamide during Attempted Nucleophilic Displacement of Chlorine in Tetrachlorophthalic Anhydride
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The interaction of tetrachlorophthalic anhydride with dimethylformamide at its reflux temperature either in the presence or absence of an aryl oxide or alkoxide furnishes predominently N,N-dimethyl-2,3,4,5-tetrachlorobenzamide (3) in contrast to the corresponding acid (4), as reported in literature.
- Ramadas, Sukuru R.,Pillai, Chandrasekaran N.,Bakthavatchalam, Rajagopal
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p. 1059 - 1060
(2007/10/02)
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- Nucleophilic Displacement in Polyhalogenoaromatic Compounds. Part 11. Kinetics of Protiodeiodination of Iodoarenes in Dimethyl Sulphoxide-Methanol
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The rates of methoxide-ion induced protiodeiodination of a number of polychloroiodobenzenes and their derivatives have been measured in dimethyl sulphoxide-methanol (9:1 v/v; 323.2 K).The true reagent under these conditions appears to be the dimethyl sulphoxide anion, and the rates of reaction in some cases appear to approach that expected of a diffusion controlled process.This corresponds to a major decrease in the efficacy of further activating substituents in the aromatic system, altough deactivating groups such as p-OMe still show large effects.Chlorine promotes protiodeiodination in the order of efficiency o-Cl > m-Cl > p-Cl; the trifluoromethyl group activates displacement in the order o-CF3 > p-CF3 > m-CF3, although with much less difference between isomeric sites. o-Nitro-groups promote protiodeiodination whereas the p-nitro-group encourages methoxydeiodination.No evidence of methoxydeiodination was found in attack of the polychloroiodobenzenes, although the rates of methoxydechlorination of the corresponding polychlorobenzenes suggest that in some cases this might occur.Evidence rejecting the possible SRN1 mechanism and supporting nucleophilic attack by a carbanionic species upon iodine is presented.
- Bolton, Roger,Moore, Clive,Sandall, John P.B.
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p. 1593 - 1598
(2007/10/02)
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- PERICYCLIC TRANSFORMATIONS OF TETRACYCLO2,903,8>TRIDECA-4,6,11-TRIENES, AND FORMATION OF DIHYDROSEMIBULLVALENES BY THERMAL INTRAMOLECULAR?4a+?2a>CYCLOADDITION IN SUBSTITUTED CYCLOOCTATRIENES
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Cyclopentadienones react with certain cyclobutene dienophiles to give the anticipated carbonyl bridge adducts; these, on relatively mild thermolysis, yield dihydrosemibullvalene derivatives by a novel sequence including cheletropic loss of carbon monoxide, electrocyclic ring opening of immediate substituted bicyclooctadienes, and intramolecular ?4a + ?2a>cycloaddition of the derived cyclooctatrienes.Other pericyclic reactions of compounds related to those of the title compounds are also discussed.
- Lay, W. P.,Mackenzie, K.,Miller, A. S.,Williams-Smith, D. L.
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p. 3021 - 3031
(2007/10/02)
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- REACTIONS OF CYCLO-OCTATETRAENE AND ITS DERIVATIVES-IX. CYCLOPENTADIENONE ADDUCTS OF TRICYCLO2,5>DECA-3,7-DIENES AND TRICYCLO2,5>NONA-3,7-DIENES
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Tetracyclo2,9.03,8>tetradeca-4,6,11-trienes 5 are produced from tricyclo2,5>deca-3,7-dienes 1 by reaction with cyclopentadienones 2 (or equiv) followed by thermal decarbonylation.With tetraphenylcyclopentadienone, however, the product 5e rearranges under the conditions required for its formation to give the dihydrosemibullvalene 11.The rearrangement evidently proceeds via the cyclo-octa-1,3,5-triene 14, the ring-opening 5e-14 being facilitated by a phenyl-conjugation effect, uncovered in another series of experiments involving the reaction of cyclopentadienone s with the tricyclo2,5>nona-3,7-diene 16.Thus the tetraphenylcyclohexa-1,3-diene 18c undergoes ring-opening in refluxing xylene to afford the cyclo-octa-1,3,5-triene 21a, whereas the dimethyldiphenyl-analogue 18b resists valence isomerisation under these conditions.
- Akhtar, Iqbal A.,Atkins, Richard J.,Fray, Gordon I.,Geen Graham R.,King, Trevor J.
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p. 3033 - 3042
(2007/10/02)
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- Sulfonation of aromatic compounds in the presence of solvents
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A process for the sulfonation of aromatic compounds wherein an aromatic substance consisting of one or more aromatic compounds susceptible to the action of sulfur trioxide is formed into a reactant by admixture with one or more organic liquids, substantially inert to sulfur trioxide under the conditions of the process, which reactant is brought to boiling at a temperature not greater than 100° C under a pressure of from 0.1 mm Hg to atmospheric pressure, gaseous sulfur trioxide is introduced thereinto thereby causing it to continue to boil, the component or components of the reactant thus volatilized is or are reconverted to liquid in a heat-exchanger and recycled to the reaction chamber, and the pressure in the reaction chamber and the rate at which the gaseous sulfur trioxide is introduced into the reactant are controlled so as to ensure that there is always present in the reaction chamber an amount of volatilizable matter exceeding that amount volatilizable by the heat of reaction of the aromatic substance present in the reaction chamber with the gaseous sulfur trioxide in contact with said aromatic substance and that the temperature of the reaction mixture is a temperature of 100° C or below.
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