Collect. Czech. Chem. Commun. 1994, 59, 1467-1471

Electrostatic Effects in Ionization Equilibria: An AM1 Study of Reversed Substituent Effect in 5-Fluorobicyclo[3.3.3]undecane-1-carboxylic Acid

Zdeněk Friedla and Stanislav Böhmb

a Faculty of Chemistry, Technical University Brno, 637 00 Brno, Czech Republic
b Department of Organic Chemistry, Prague Institute of Chemical Technology, 166 28 Prague 6, Czech Republic


Relative proton transfer enthalpies δ ∆H0 of sp and ap conformers of 5-fluorobicyclo[3.3.3]undecane-1-carboxylic acid have been calculated by the AM1 method and the results were compared with the prediction of the electrostatic theory. It is shown that the great reversed substituent effect in the sp conformer (δ ∆H0 = 32.1 kJ mol-1) is substantially overestimated largely due to sterical Baeyer strain and non-bonded interactions.