The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Wojciech Dmowski - One of the best experts on this subject based on the ideXlab platform.
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Dehydrobromination of trans 3 4 dibromo 7 7 9 9 tetrafluoro 8 oxa cis bicyclo 4 3 0 nonane a route to bicyclic fluoroalkenes and 7 7 9 9 tetrafluoro 8 oxa cis bicyclo 4 3 0 nona 2 4 diene
ChemInform, 2010Co-Authors: Ireneusz Nowak, Wojciech DmowskiAbstract:Abstract Dehydrobromination of trans-3,4-dibromo-7,7,9,9-tetrafluoro-8-oxa-cis-bicyclo[4.3.0] -nonane (1) was studied under a variety of conditions. In alkaline media, 3-bromo-7,7,9,9-tetrafluoro-8-oxa-cis-bicyclo[4.3.0]non-3-ene (2) and/or 1,3,3-trifluoro-1,3-dihydroisobenzofuran (3) were formed in ratios depending on the nature of the base and its concentration. Vacuum pyrolysis of 1 gave 7,7,9,9-tetrafluoro-8-oxa-cis-bicyclo[4.3.0]nona-2,4-diene (7) as the main product.
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sodium dithionite initiated addition of 1 bromo 1 chloro 2 2 2 trifluoroethane to β pinene synthesis of cf3 substituted terpenoids
Journal of Fluorine Chemistry, 2004Co-Authors: Wojciech Dmowski, Jolanta Ignatowska, Krystyna PiaseckamaciejewskaAbstract:Abstract Sodium dithionite effectively promotes the addition of 1-bromo-1-chloro-2,2,2-trifluoroethane to the exocyclic double bond of β-pinene. The reaction proceeded in an MeCN/H 2 O system to give almost quantitatively a 1:1 mixture of diastereoisomers of 4-(2-bromoisopropyl)-1-(2-chloro-3,3,3-trifluoropropyl)-cyclohexene ( 1 ). Dehydrobromination of 1 with pyridine gave a mixture of regioisomeric dienes 2 and 3 , while treatment with DBU at elevated temperature resulted in total dehydrohalogenation to give trienes 4 and 5 . Reduction of 1 with Bu 3 SnH gave 1-(2-chloro-3,3,3-trifluoropropyl)-4-(isopropyl)cyclohexene ( 6 ) which on dehydrochlorination with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) afforded conjugated diene, 4-isopropyl-1-( trans -3,3,3-trifluoropropenyl)-cyclohexene ( 7 ), with 50% overall yield. All the transformations proceeded with the retention of configuration at the carbon atom C-4 and the final compound 7 exhibited high optical activity.
Jinchang Liu - One of the best experts on this subject based on the ideXlab platform.
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effects of bromination Dehydrobromination on the microstructure of isotropic pitch precursors for carbon fibers
Polymers, 2020Co-Authors: Dingcheng Liang, Qiang Xie, Deqian Liu, Shuai Yang, Jinchang LiuAbstract:In this work, isotropic pitch precursors are synthesized by the bromination-debromination method with ethylene bottom oil (EO) as the raw material and bromine as the initiator for pitch formation and condensation reactions. The aggregation structure, molecular weight distribution, and molecular structure of isotropic pitch precursors are characterized by thermal mechanical analyzer (TMA), MALDI TOF-MS, and 13C NMR, respectively, for revealing the mechanism of synthesis of isotropic pitch precursors. The results show that at low bromine concentrations, polycyclic aromatic hydrocarbons (PAHs) were mainly ordered in cross-linked structures by bromination-debromination through substitution reactions of side chains. The condensed reactivity can be improved by the effect of bromine, meaning that condensation reaction was aggravated by the method of bromination-Dehydrobromination. In the presence of excess bromine, the cross-linked stereo structure of PAHs changed to the planar structure of condensed PAHs, which was not conducive to the subsequent spinning and preparation of carbon fibers.
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controllable synthesis of isotropic pitch precursor for general purpose carbon fiber using waste ethylene tar via bromination Dehydrobromination
Journal of Cleaner Production, 2020Co-Authors: Jinchang Liu, Xujun Chen, Qiang Xie, Dingcheng LiangAbstract:Abstract Nowadays, the substantial amount of waste ethylene tar (ET) lacks a clean and efficient route for utilization. In this work, a feasible approach was developed to fabricate general purpose carbon fiber (GPCF) using ET as a raw material. The method of bromination–Dehydrobromination was used to synthesize controllably isotropic pitch precursor for GPCF. The results show that bromination–Dehydrobromination reaction promotes the cyclization and aromatization of small molecules and relatively low molecular weight components and also prevents excess condensation during thermal treatment. The molecular structure of pitch precursor generated from bromination–Dehydrobromination reaction has more linear and cross-linked structures as more naphthenic groups and the side chain of aromatic rings. The spinnability of pitch precursors and the mechanical performance of GPCFs are optimized when 10 wt% of bromine is introduced in synthetic reaction. The tensile strength, Young’s modulus, and elongation property of the final GPCF are 1072 ± 66 MPa, 47 ± 7 GPa, and 2.3%, respectively, with the diameter of 10.3 ± 0.5 μm.
Dingcheng Liang - One of the best experts on this subject based on the ideXlab platform.
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effects of bromination Dehydrobromination on the microstructure of isotropic pitch precursors for carbon fibers
Polymers, 2020Co-Authors: Dingcheng Liang, Qiang Xie, Deqian Liu, Shuai Yang, Jinchang LiuAbstract:In this work, isotropic pitch precursors are synthesized by the bromination-debromination method with ethylene bottom oil (EO) as the raw material and bromine as the initiator for pitch formation and condensation reactions. The aggregation structure, molecular weight distribution, and molecular structure of isotropic pitch precursors are characterized by thermal mechanical analyzer (TMA), MALDI TOF-MS, and 13C NMR, respectively, for revealing the mechanism of synthesis of isotropic pitch precursors. The results show that at low bromine concentrations, polycyclic aromatic hydrocarbons (PAHs) were mainly ordered in cross-linked structures by bromination-debromination through substitution reactions of side chains. The condensed reactivity can be improved by the effect of bromine, meaning that condensation reaction was aggravated by the method of bromination-Dehydrobromination. In the presence of excess bromine, the cross-linked stereo structure of PAHs changed to the planar structure of condensed PAHs, which was not conducive to the subsequent spinning and preparation of carbon fibers.
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controllable synthesis of isotropic pitch precursor for general purpose carbon fiber using waste ethylene tar via bromination Dehydrobromination
Journal of Cleaner Production, 2020Co-Authors: Jinchang Liu, Xujun Chen, Qiang Xie, Dingcheng LiangAbstract:Abstract Nowadays, the substantial amount of waste ethylene tar (ET) lacks a clean and efficient route for utilization. In this work, a feasible approach was developed to fabricate general purpose carbon fiber (GPCF) using ET as a raw material. The method of bromination–Dehydrobromination was used to synthesize controllably isotropic pitch precursor for GPCF. The results show that bromination–Dehydrobromination reaction promotes the cyclization and aromatization of small molecules and relatively low molecular weight components and also prevents excess condensation during thermal treatment. The molecular structure of pitch precursor generated from bromination–Dehydrobromination reaction has more linear and cross-linked structures as more naphthenic groups and the side chain of aromatic rings. The spinnability of pitch precursors and the mechanical performance of GPCFs are optimized when 10 wt% of bromine is introduced in synthetic reaction. The tensile strength, Young’s modulus, and elongation property of the final GPCF are 1072 ± 66 MPa, 47 ± 7 GPa, and 2.3%, respectively, with the diameter of 10.3 ± 0.5 μm.
Gwilherm Evano - One of the best experts on this subject based on the ideXlab platform.
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synthesis of ketene n n acetals by copper catalyzed double amidation of 1 1 dibromo 1 alkenes
Organic Letters, 2009Co-Authors: Alexis Coste, Francois Couty, Gwilherm EvanoAbstract:An efficient procedure for the preparation of ketene N,N-acetals by copper-catalyzed double amidation of 1,1-dibromo-1-alkenes is reported. The reaction was found to be general, and ketene aminals could be obtained in good yields when potassium phosphate in toluene was used at 80 °C. The reaction was found to proceed through a regioselective monocoupling reaction followed by Dehydrobromination and hydroamidation.
Ireneusz Nowak - One of the best experts on this subject based on the ideXlab platform.
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Dehydrobromination of trans 3 4 dibromo 7 7 9 9 tetrafluoro 8 oxa cis bicyclo 4 3 0 nonane a route to bicyclic fluoroalkenes and 7 7 9 9 tetrafluoro 8 oxa cis bicyclo 4 3 0 nona 2 4 diene
ChemInform, 2010Co-Authors: Ireneusz Nowak, Wojciech DmowskiAbstract:Abstract Dehydrobromination of trans-3,4-dibromo-7,7,9,9-tetrafluoro-8-oxa-cis-bicyclo[4.3.0] -nonane (1) was studied under a variety of conditions. In alkaline media, 3-bromo-7,7,9,9-tetrafluoro-8-oxa-cis-bicyclo[4.3.0]non-3-ene (2) and/or 1,3,3-trifluoro-1,3-dihydroisobenzofuran (3) were formed in ratios depending on the nature of the base and its concentration. Vacuum pyrolysis of 1 gave 7,7,9,9-tetrafluoro-8-oxa-cis-bicyclo[4.3.0]nona-2,4-diene (7) as the main product.