- NATURE AND CONCENTRATION OF ACTIVE SPECIES IN CATIONIC POLYMERIZATION OF VINYL ETHERS: A KINETIC INVESTIGATION
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The Kinetics of the polymerization of isopropyl vinyl ether, isobutyl vinyl ether (IBVE) and chloroethyl vinyl ether initiated by HI in CH2Cl2, in the presence and in the absence of tetrabutylammonium iodide as common anion salt, were investigated.The polymerizations proceed directly through the carbon-iodide termini without any necessary electrophilic activator.As previously observed with cyclohexyl vinyl ether, it was found that the addition of small amounts of salt, (0.5-10percent with respect to initial , depending on the monomer) drastically reduces the polymerization rate and leads to living-type polymerizations.Higher amounts of salt have no influence on the polymerization rate which remains constant over a broad range of / ratios.This general behaviour, observed for the all vinyl ethers, suggests a common ion salt effect and therefore an ionic polymerization mechanism involving ion pairs and free ions.In the absence of salt, both ion pairs and free ions of higher reactivity participate in the propagation, whereas only ion pairs contribute to the propagation in the presence of a common ion salt.According to this scheme, the living character of the polymerization is assumed to result from a propagation reaction governed by undissociated ionic species.The validity and the implications of this reaction scheme, in terms of active centre concentrations, are also discussed.
- Cramail, Henri,Deffieux, Alain
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- Nucleophilic addition to acetylenes in superbasic catalytic systems: XIII. Fluoride cesium containing systems, efficient catalysts for alkanols vinylation
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New catalytic systems CsF-MOH (M = Li, Na) were developed for the synthesis of alkyl vinyl ethers comparable in efficiency to cesium alcoholates. The addition of primary and secondary alcohols to acetylene occurs in the presence of these systems at the atmospheric (DMSO, 100°C) or at enhanced (without solvent, 135-140°C) acetylene pressure and affords alkyl vinyl ethers in up to 93% yield. 2005 Pleiades Publishing, Inc.
- Oparina,Shaikhudinova,Parshina,Vysotskaya,Preiss,Henkelmann,Trofimov
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p. 656 - 660
(2007/10/03)
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- Nucleophilic Addition to Acetylenes in Superbasic Catalytic Systems. VII. Vinylation of Lower Alcohols
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Superbasic systems KOH-DMSO and KOH-HMPA with acetylene and alcohols form highly active catalytic complexes capable of sharply increasing the rate and selectivity of nucleophilic addition of alcohols to acetylene and allowing preparation of high-purity lower alkyl vinyl ethers in high yield under acetylene pressure equal to atmospheric.
- Trofimov, B. A.,Oparina, L. A.,Lavrov, V. I.,Parshina, L. N.
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p. 597 - 600
(2007/10/03)
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- Dissociation of Positively Charged Aliphatic Epoxides. II. +. Epoxides and α,β Unsaturated Ethers
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The unimolecular dissociations of C5 epoxides ions mono- or disubstituted at C1 give exclusive loss of CH3 and exclusive formation of methoxyvinyl carbenium ion, both in the source and in the 2nd field-free region.In the case of the 1,2-disubstituted ion in the 2nd field-free region the loss of ethene is the only pathway, while a competition occurs for the trisubstituted ion leading to +. and +. ions, the structure of which are demonstrated.The first step of the different mechanisms is the cleavage of the heterocyclic C-C bond.
- Bouchoux, Guy,Djazi, Feycal,Hoppilliard, Yannik,Jaudon, Pascale,Nouts, Nathalie
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- DIVINYL SULFOXIDE. V.* BASE-CATALYSED ADDITION OF ALCOHOLS AND THERMOLYSIS OF THE ADDUCTS
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β-Alkoxyethyl vinyl sulfoxides and bis(β-alkoxyethyl) sulfoxides were obtained and characterized for the first time as a result of nucleophilic addition of alcohols to divinyl sulfoxide.When heated (280-290 deg C), the β-alkoxyethyl vinyl sulfoxides are cleaved, forming alkyl vinyl ethers, and divinyl sulfoxide can consequently be used as a convenient CH2=CH+ synthon.
- Gusarova, N. K.,Trofimov, B. A.,Efremova, G. G.,Amosova, S. V.
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p. 2028 - 2033
(2007/10/02)
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