Mechanism of the protonation of azulenes in aqueous solutions of acids

Autor:	Yu. A. Ershov, Yu. A. Mikheev, L. N. Guseva
Rok vydání:	2013
Předmět:	chemistry.chemical_compound Aqueous solution Hammett acidity function Polymerization Chemistry Supramolecular chemistry Cationic polymerization Protonation Physical and Theoretical Chemistry Azulene Photochemistry Reversible reaction
Zdroj:	Russian Journal of Physical Chemistry A. 87:1645-1653
ISSN:	1531-863X 0036-0244
Popis:	In aqueous solutions of strong acids (H2SO4, H3PO4, and HCl) containing azulene, the fast reversible protonation of azulene is accompanied by the slow formation of a disperse dark violet dye insoluble in acids, alcohol, and heptane. On the basis of the kinetic specifics of this reaction and the nonlinear (nearly reciprocal quadratic) dependence of the concentrations ratio of their cationic and neutral forms on the Hammett acidity function known for azulene and 14 of its derivatives, azulene is shown not to be a Hammett base. A mechanism for the reversible reactions of the azulenium cation is proposed that considers supramolecular dimers to be the basic state of azulene and its derivatives. The scheme includes reactions of the unstable intermediate π complexes formed from the dimers and hydrated hydrogen cations; the complexes quickly dissociate in the opposite direction and react with the hydrated protons to yield azulenium cations and unstable molecules that induce polymerization of the dimers.
Databáze:	OpenAIRE
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