Surface Mediated Hydride Transfer Reaction of a Diarylmethyl Head Group Functionalized Poly(isobutyl vinyl ether) with Triphenylmethylium

Spange, Stefan; Eismann, Ulrike

doi:10.1002/1521-3935(20010301)202:6<900::aid-macp900>3.0.co;2-j

Macromol. Chem. Phys.

2001

DOI: 10.1002/1521-3935(20010301)202:6<900::aid-macp900>3.0.co;2-j

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Surface Mediated Hydride Transfer Reaction of a Diarylmethyl Head Group Functionalized Poly(isobutyl vinyl ether) with Triphenylmethylium

Stefan Spange¹,

Ulrike Eismann

Abstract: Poly(isobutyl vinyl ether) (PIBVE) with bis(4‐methoxyphenyl)methyl‐head‐group is transformed into a cationically active macro initiator by a hydride transfer reaction with silica surface coordinated triphenylmethylium as the hydride acceptor. The formation of the macrocation is investigated directly by UV/Vis spectroscopy on the surface of the silica particles and by GPC analysis of the surrounding solution. The hydride transfer reaction can be observed on the surface of the silica in a narrow temperature wind… Show more

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Cited by 4 publications

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Surface Functionalization of Silica with 2‐Vinylfuran by Cationic Polymerization

Höhne¹,

Spange²

2003

Macro Chemistry & Physics

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Cationic surface polymerization of 2‐vinylfuran with chlorotriphenylmethane as initiator has been used for the functionalization of silica particles. The influence of monomer/initiator ratio and temperature on grafting efficiency, yield, and degree of grafting has been investigated. Grafting efficiency is a significant function of temperature and monomer/initiator ratio, because crosslinking reactions between cationically active chains increases the amount of the immobilized polyvinylfuran fraction. Thus, larger initiator concentrations on the silica cause higher polymer content on the surface. Polymer structure elucidation and surface properties are analyzed by means of solid‐state NMR spectroscopy, UV‐vis spectroscopy, BET – measurements, and scanning electron microscopy.

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Surface Functionalization of Silica with 2‐Vinylfuran by Cationic Polymerization

Höhne¹,

Spange²

2003

Macro Chemistry & Physics

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Synthesis of Inorganic/Organic Host−Guest Hybrid Materials by Cationic Vinyl Polymerization within Y Zeolites and MCM-41

et al. 2001

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Cationic guest polymerizations of several vinyl monomers inside the pores of HY zeolites and MCM-41 as hosts have been used for the synthesis of novel organic/inorganic hybrid materials. Substituted vinyl ethers [ROCHCH2; R = −CH2CH(CH3)2, −C2H5, −C2H4Cl, −C6H11], 2,3-dihydrofuran, and N-vinylcarbazole can serve this purpose, because their polymerization can be initiated by the active protons in HY zeolite or by coadsorbed arylmethylium ions in MCM-41. The synthesis of well-defined poly(vinyl ethers) or poly(vinylcarbazole) under the conditions of constricted geometry can be achieved by means of cationic host−guest polymerization of the corresponding monomers in MCM-41 (pore diameter 3.6 nm) with (4-CH3OC6H4)2CHCl (MeO) or (C6H5)3CCl (TC) as the internal surface initiator. The reaction products are novel polymer/MCM-41 host−guest hybrid materials. The molecular mass of the (enclosed) polymer and the percentage of polymer within the pores of MCM-41 as well as HY zeolite can be adjusted within certain limits. Polymeric products are analyzed by solid-state magic angle spinning cross-polarization 13C{1H} NMR spectroscopy and gel permeation chromatography analyses of the obtained polymer fraction after dissolution of the hybrid material in an aqueous potassium hydroxide solution. The formation of conjugated sequences of poly(vinyl ether) segments inside the HY zeolites is caused by successive ether cleavage along the encapsulated polymer chains.

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Reactions of Carbocations with Unsaturated Hydrocarbons: Electrophilic Alkylation or Hydride Abstraction?

2002

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Benzhydryl cations were used as reference electrophiles to determine the hydride donor reactivities of unsaturated hydrocarbons. The kinetics of the reactions were followed by UV-vis spectroscopy and conductivity measurements, and it was found that the second-order rate constants for the hydride transfer processes were almost independent of the solvents or counterions employed. The rate constants correlate linearly with the previously published empirical electrophilicity parameters E of the benzhydrylium ions. Therefore, the linear free energy relationship log k(20 degrees C) = s(E + N) could be employed to characterize the hydride reactivities of the hydrocarbons by the nucleophilicity parameters N and s. The similarity of the slopes s for hydride donors and pi-nucleophiles allows a direct comparison of the reactivities of these different functional groups based on their nucleophilicity parameters N. Since nucleophilicity parameters of -5 < N < 0 have been found for a large variety of allylic and bisallylic hydride donors, a rule of thumb is derived that hydride transfer processes may compete with carbon-carbon bond-forming reactions when carbocations are combined with olefins of pi-nucleophilicity N < 0.

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Surface Mediated Hydride Transfer Reaction of a Diarylmethyl Head Group Functionalized Poly(isobutyl vinyl ether) with Triphenylmethylium

Cited by 4 publications

References 11 publications

Surface Functionalization of Silica with 2‐Vinylfuran by Cationic Polymerization

Surface Functionalization of Silica with 2‐Vinylfuran by Cationic Polymerization

Synthesis of Inorganic/Organic Host−Guest Hybrid Materials by Cationic Vinyl Polymerization within Y Zeolites and MCM-41

Reactions of Carbocations with Unsaturated Hydrocarbons: Electrophilic Alkylation or Hydride Abstraction?

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