The gas-phase reaction of pI-Me3SiC6H4(CH2)(3)C6H5 (p-TSDPP) with gaseous cations, including C2H5+, Me2Cl+ and DCO-, has been studied in the pressure range from 10(-8) to 10(3) Torr by Fourier-transform ion cyclotron resonance (FT-ICR) and by the radiolytic technique. The protonated or alkylated intermediates undergo intramolecular migration and intermolecular transfer of protons and/or Me3Si+. The results underline the role of the spectator ring in providing internal solvation to an arenium moiety, as evidenced by the noticeable stability towards Me3Si loss with respect to a single-ring model substrate, p-Me3SiC6H4Me (p-TST), upon reaction with the same gaseous ions. The extent of the alkylation route relative to the alkyldesilylation processes, measured as a function of the arenium ion lifetime, permits derivation of the rate constant for the conversion by proton transfer of the originally formed arenium ions to ipso-silylated isomers (ki). The estimated values of k(i(p-TST))= 5 x 10(9) s(-1) and k(i(p-TSDPP)) = 2 X 10(8) s(-1) at 120 degrees C suggest that intraannular H shifts are faster than ring-to-ring H transfer, in agreement with previous evidence from tert-butylated arenium ions. The reactivity of [Me3Si-arene](+) adducts, adequately described by the Wheland sigma-complex model, does not exclude the intermediacy of an ion-neutral noncovalent complex.

The gas-phase reactivity of p-Me3Si-substituted 1,3-diphenylpropane towards charged electrophiles: intra- and interannular hydrogen migrations / Crestoni, Maria Elisa. - In: CHEMISTRY-A EUROPEAN JOURNAL. - ISSN 0947-6539. - STAMPA. - 4(1998), pp. 993-999. [10.1002/(SICI)1521-3765(19980615)4:6<993::AID-CHEM993>3.0.CO;2-I]

The gas-phase reactivity of p-Me3Si-substituted 1,3-diphenylpropane towards charged electrophiles: intra- and interannular hydrogen migrations

CRESTONI, Maria Elisa
1998

Abstract

The gas-phase reaction of pI-Me3SiC6H4(CH2)(3)C6H5 (p-TSDPP) with gaseous cations, including C2H5+, Me2Cl+ and DCO-, has been studied in the pressure range from 10(-8) to 10(3) Torr by Fourier-transform ion cyclotron resonance (FT-ICR) and by the radiolytic technique. The protonated or alkylated intermediates undergo intramolecular migration and intermolecular transfer of protons and/or Me3Si+. The results underline the role of the spectator ring in providing internal solvation to an arenium moiety, as evidenced by the noticeable stability towards Me3Si loss with respect to a single-ring model substrate, p-Me3SiC6H4Me (p-TST), upon reaction with the same gaseous ions. The extent of the alkylation route relative to the alkyldesilylation processes, measured as a function of the arenium ion lifetime, permits derivation of the rate constant for the conversion by proton transfer of the originally formed arenium ions to ipso-silylated isomers (ki). The estimated values of k(i(p-TST))= 5 x 10(9) s(-1) and k(i(p-TSDPP)) = 2 X 10(8) s(-1) at 120 degrees C suggest that intraannular H shifts are faster than ring-to-ring H transfer, in agreement with previous evidence from tert-butylated arenium ions. The reactivity of [Me3Si-arene](+) adducts, adequately described by the Wheland sigma-complex model, does not exclude the intermediacy of an ion-neutral noncovalent complex.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/458429
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