- Compositions containing ionic liquids and their uses, in particular in organic synthesis
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An ionic liquid is used as liquid matrix for organic synthesis in homogeneous phase on soluble support, the ionic liquid being presented in liquid or solid form at ambient temperature, of formula A1+X1?, A1+ representing a cation, functional or non-functional, or a mixture of cations in which either none of the cations is functional or at least one of the cations is functional, and X1? an anion, functional or non-functional, or a mixture of anions in which either none of the anions is functional or at least one of the anions is functional.
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Page/Page column 32
(2016/10/17)
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- Side-chain-type anion exchange membranes bearing pendant quaternary ammonium groups: Via flexible spacers for fuel cells
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To realize high performance anion exchange membranes (AEMs) for alkaline fuel cells (AFCs), a series of quaternized poly(ether sulfone)s (PESs) with different lengths of flexible spacers linking cationic groups and the backbone was synthesized via nucleophilic polycondensation, demethylation and Williamson reactions. Atomic force microscopy (AFM) phase images show clear hydrophilic/hydrophobic phase separation for all the side-chain-type AEMs. The PES-n-QA membrane with hexyleneoxy spacers (n = 6) between the cationic groups and backbone (benzene ring) exhibited the maximum conductivity of 62.7 mS cm-1 (IEC = 1.48 meq. g-1) at 80 °C. The AEM materials are found to have an improved long-term alkaline stability by extending the length of the flexible spacer (n ≥ 4). The PES-12-QA membrane with a flexible dodeceneoxy spacer demonstrated the highest alkaline stability, where the conductivity and IEC only decreased by 8.1% and 6.9% after immersing in a 1 M aqueous KOH solution at 60 °C for 720 h. Furthermore, the single fuel cell performance test using PES-6-QA as an AEM showed a maximum power density of 108.3 mW cm-2 at a current density of 250 mA cm-2 at 60 °C.
- Lin, Chen Xiao,Huang, Xiao Ling,Guo, Dong,Zhang, Qiu Gen,Zhu, Ai Mei,Ye, Mei Ling,Liu, Qing Lin
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p. 13938 - 13948
(2016/10/30)
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- Intramolecular Halogen Transfer via Halonium Ion Intermediates in the Gas Phase
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The fragmentation of halogen-substituted protonated amines and quaternary ammonium ions (R1R2R3N+CH2(CH2)nX, where X = F, Cl, Br, I, n = 1, 2, 3, 4) was studied by electrospray ionization tandem mass spectrometry. A characteristic fragment ion (R1R2R3N+X) resulting from halogen transfer was observed in collision-induced dissociation. A new mechanism for the intramolecular halogen transfer was proposed that involves a reactive intermediate, [amine/halonium ion]. A potential energy surface scan using DFT calculation for CH2-N bond cleavage process of protonated 2-bromo-N,N-dimethylethanamine supports the formation of this intermediate. The bromonium ion intermediate-involved halogen transfer mechanism is supported by an examination of the ion/molecule reaction between isolated ethylenebromonium ion and triethylamine, which generates the N-bromo-N,N,N-triethylammonium cation. For other halogens, Cl and I also can be involved in similar intramolecular halogen transfer, but F cannot be involved. With the elongation of the carbon chain between the halogen (bromine as a representative example) and amine, the migration ability of halogen decreases. When the carbon chain contains two or three CH2 units (n = 1, 2), formal bromine cation transfer can take place, and the transfer is easier when n = 1. When the carbon chain contains four or five CH2 units (n = 3, 4), formal bromine cation transfer does not occur, probably because the five- and six-membered cyclic bromonium ions are very stable and do not donate the bromine to the amine.
- Chai, Yunfeng,Xiong, Xingchuang,Yue, Lei,Jiang, You,Pan, Yuanjiang,Fang, Xiang
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p. 161 - 167
(2015/12/30)
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- Facile synthesis of (ω-bromoalkyl)trimethylammonium bromides
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Reaction of a 1,ω-dibromoalkane with trimethylamine in THF at room temperature precipitates the corresponding (ω-bromoalkyl)trimethylammonium bromide to cleanly form the mono-substituted product in the absence of the bis-quat salt.
- Bartsch, Richard A.,Zhao, Wenyi,Zhang, Zhi-Yi
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p. 2393 - 2398
(2007/10/03)
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- Potent acetylcholinesterase inhibitors: Design, synthesis, and structure - Activity relationships of bis-interacting ligands in the galanthamine series
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New galanthamine derivatives, especially bis-interacting ligands 3-5 and 7-9 were prepared in order to interact with the catalytic and the peripheral sites of acetylcholinesterase (AChE). The synthesis, the anticholinesterase activities, and the structure-activity relationships of bis-interacting ligands are reported. Compounds 4d-e were found to be more potent than galanthamine and tacrine in inhibiting AChE. Copyright (C) 1998 Elsevier Science Ltd.
- Mary, Aude,Renko, Dolor Zafiarisoa,Guillou, Catherine,Thal, Claude
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p. 1835 - 1850
(2007/10/03)
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- DEPROTONATION OF HYDRAZINIUM DICATIONS IN THE DIAZONIAPROPELLANE SERIES TO FORM BRIDGEHEAD IMINIUM IONS; EXTERNAL AND INTRAMOLECULAR TRAPPING
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The reactions of hexa-alkylhydrazinium dications with bases and nucleophiles are described. 1,5-Diazonia-tricyclodecane (1) is hydrolysed rapidly by SN2 attack on the four-membered ring with ring opening (C-N+ cleavage).In all other cases deprotonation at α-C with concomitant N+-N+ cleavage (E2 reaction) is the only primary process.The cis-1,6-dimethyl-1,6-diazoniabicyclodecane ion (6), is exclusively deprotonated at a methyl group (Hofmann orientation). 1,5-Diazoniatricycloundecane (2), 1,6-diazoniatricyclododecane (3), 1,6-diazoniatricyclotridecane (4), and 1,6-diazoniatricyclotetradecane (5) ions generate bridgehead iminium ions, which may be trapped intramolecularly by the transannular amino group or externally by added nucleophiles.Reaction with cyanide ion gives detailed information on the regio- and stereo-chemistry of the trapping sequence.Although intramolecular/external trapping is truly competitive, the products of these reactions (α-amino-ammonium ions and α-aminonitriles) may be interconverted under different reaction conditions.The solvolysis of 1-(3-phenoxypropyl)-1,5-diazabicyclooctanium bromide in aqueous 48percent HBr is 103 faster than that of 3-phenoxypropyltrimethylammonium bromide, and the products are consistent with the intermediacy of the dication (2).These observations provide an explanation for the formation of 1,5-diazacyclo-octane in the reaction of 1,3-dibromopropane with hydrazine.
- Alder, Roger W.,Sessions, Richard B.,Gmuender, John O.,Grob, Cyril A.
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p. 411 - 418
(2007/10/02)
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