- Regularities of Pd/C-catalyzed reduction of trichlorobiphenyls with 2-propanol in basic medium
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Reduction of a series of trichlorobiphenyls with 2-propanol in basic medium catalyzed by Pd/C has been studied. Regioselectivity of the reduction has been determined. In the studied cases, the chlorine atom in para or meta positions of the more substituted ring has been more reactive. Using isotope labeling, it has been demonstrated that the reaction occurs via the stage of 2-propanol dehydration on palladium catalyst, followed by catalytic hydrogenation of the polychlorinated biphenyls.
- Kostenko,Eliseenkov,Petrov
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p. 1656 - 1662
(2017/09/25)
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- A new advanced method for heterogeneous catalysed dechlorination of polychlorinated biphenyls (PCBs) in hydrocarbon solvent
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The dechlorination of PCBs with solid hydrazine hydrochloride catalysed by palladium, in an organic solvent, yields biphenyl in short reaction times. The catalyst system can be efficiently reused for several cycles. Ultrasonication of the heterogeneous catalysed reaction increases the dechlorination rate remarkably. The reactivity of the C-Cl bond on the PCB ring are in the order meta>para?ortho.
- Rodríguez, J. Gonzalo,Lafuente, Antonio
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p. 9581 - 9583
(2007/10/03)
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- Dechlorination of hexachlorobiphenyl by using potassium-sodium alloy
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2,2',4,4',5,5'-Hexachlorobiphenyl (HCB) was dechlorinated with potassium-sodium (K-Na) alloy under an inert gas atmosphere. Solvent effect was observed in the reaction. Dechlorination yields in benzene and cyclohexane were 99.9998% and 99.99996%, respecti
- Miyoshi, Kumiko,Nishio, Takehiko,Yasuhara, Akio,Morita, Masatoshi
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p. 819 - 824
(2007/10/03)
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- Polychlorinated biphenyl reductive dechlorination by vitamin B12s: Thermodynamics and regiospecificity
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Microbial reductive dechlorination reactions play an important role in determining the environmental fate of polychlorinated biphenyls (PCBs), especially for PCB congeners with more than four chlorines. Powerful chemical catalysts such as vitamin B12s provide an effective tool for the study of reductive dechlorination reactions. The reductive dechlorination of PCBs by titanium(III) citrate-reduced vitamin B12s was studied in batch reactors. Long-term experiments demonstrated reductive dechlorination of aqueous and sediment-sorbed 2,3,4,5,6-pentachlorobiphenyl (2,3,4,5,6-PeCB) to tetra-, tri-, di-, and monochlorobiphenyl products. Approximately 10% chlorine removal was observed in 36 days in aqueous experiments at 20°C; the sediment experiment showed 40% chlorine removal in 42 days at 30°C. Nearly all possible intermediates were produced and reductively dechlorinated, with no apparent accumulation of individual congeners. Short-term experiments were conducted to determine the pathway forvitamin B12s-catalyzed reductive dechlorination of aqueous 2,3,4,5,6-PeCB and its dechlorinated products; relative product distributions were measured for all possible tetra-and trichlorobiphenyl reductive dechlorination reactions. Theoretical product distributions based on free energies of formation agreed with observed product distributions for short-and long-term experiments. Reductive dechlorination was favored at positions with adjacent chlorines; on average, chlorines were removed equally from ortho, meta, and para positions.
- Woods, Sandra L.,Trobaugh, Darin J.,Carter, Kim J.
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p. 857 - 863
(2007/10/03)
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- Palladium-catalyzed carbonylative cross-coupling of organoboranes with hypervalent iodonium salts: Synthesis of aromatic ketones
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The cross-coupling reaction of organoboronic acids and carbon monoxide (1 atm) with aryl-, alkenyl-, and alkynyliodonium salts at room temperature afforded unsymmetric aromatic ketones in moderate yields.
- Kang, Suk-Ku,Lim, Kwon-Ho,Ho, Pil-Su,Yoon, Seok-Keun,Son, Hoe-Joo
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p. 1481 - 1489
(2007/10/03)
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- Hydrogenolysis of polychlorinated biphenyls by sodium borohydride with homogeneous and heterogeneous nickel catalysts
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The hydrogenolysis (hydrodechlorination) of a series of pure PCB congeners with sodium borohydride was studied. In the absence of nickel compounds, very little reaction occurred, but in the presence of solid Raney-type nickel or in the presence of a soluble Ni(0)triphenylphosphine complex, extensive hydrogenolysis occurred at ambient temperatures in DMF. The selectivity of one congener versus another was studied and found to be low. The selectivity for 2-, 3-, and 4-chloro displacement from di- and trichlorobiphenyls in the presence of Ni(0) complexes, however, was found to be high. The selectivities are interpreted with respect to the known mechanism of oxidative addition of aryl halides with Ni(0) complexes.
- Roth,Dakoji,Hughes,Carmody
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- Etude du Comportement Photochimique de quelques Diaryl-1,3-triazenes
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The photolysis of Diaryl-1,3-triazenes gives products whose structures are consistent with a cage recombination process of homolytically formed radicals and subsequent abstraction of hydrogen from the solvent molecules by arylamino radicals.In aromatic solvents, a free-radical chain process leads to the formation of products resulting from the homolytic substitution on the solvent.Quenching experiments show that singlet and triplet excited states are reactive but that intersystem crossing efficiency is low.
- Julliard, Michel,Vernin, Gaston,Metzger, Jacques
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p. 456 - 466
(2007/10/02)
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