title: Solvent Effects on the Equilibrium between Localized and Delocalized States of Thermochromic Semibullvalenes and Barbaralanes.
abstract: The position of the equilibrium between localized and delocalized states of thermochromic semibullvalenes and barbaralanes (see the Equation) depends strongly on the solvent. Dipolar aprotic solvents, particularly N,N'-dimethylpropylene urea, favor the delocalized, bishomoaromatic state (ΔH(0) =8 kJ mol(-1) (cyclohexane), ΔH(0) <0 kJ mol(-1) (N,N'-dimethylpropylene urea)).
authors.affiliation: Institut für Organische Chemie der Universität, Am Hubland, D-97074 Würzburg, Germany, Fax: (+49) 931-888-4606. seefelde@chemie.uni-wuerzburg.de.
authors.forename: M
authors.initials: M
authors.lastname: Seefelder
authors.forename: H
authors.initials: H
authors.lastname: Quast
keywords: Cope rearrangements; Homoaromaticity; Solvent effects; Transition states; Valence isomerization