1,721,190 research outputs found
Probing Ions from Simple Aromatic Molecules by Reactivity and by Spectroscopy
No full textInvited lectur
Mechanistic views on aromatic substitution reactions by gaseous cations
No full textRecent advances in the understanding of the gas-phase reaction
of aromatics with cationic electrophiles in a thermally equilibrated domain are described. The overall substitution reaction is analyzed in terms of its elementary steps. Their contribution to the overall reactivity pattern is dissected by the use of selected systems, which allowed one to highlight the kinetic role of single elementary events. Mechanistic studies have focused on the structure and reactivity of covalent and non-covalent ionic intermediates, which display a rich chemistry and provide benchmark reactivity models. Particular interest has been devoted to proton transfer reactions, which may occur in either an intra- or intermolecular fashion in arenium intermediates. A quantitative study of their rates and associated kinetic isotope effects is reported
Vinylation of Aromatic Substrates by Free Unsolvated Vinyl Cation in the Gaseous and Liquid Phase
No full textAromatic Acylation in Homogeneous solution and in the Gas Phase: the Mechanistic Relevance of the Mesitylene/durene Reactivity Ratio
No full textBy means of a mixed acetic-trifluoroacetic anhydride a scale of relative substrate reactivity for aromatic acetylation is obtained, which spans over eight powers of ten from benzene to 2-methylthiophene. Correlation of these reactivity data with relevant substrate parameters is attempted, to gain an understanding of the possible nature of the electrophilic substitution mechanism at work, i.e. either an ionic (two-electron) or a single-electron route. The study includes gas-phase reactivity data on the reaction of free acetylium ion, which has been generated by a radiolytic method. From this comparative approach a 'conventional' ionic mechanism for the aromatic acetylation reaction is substantiated
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