ELECTROSTATIC EFFECTS IN IONIZATION EQUILIBRIA - AN AM1 STUDY OF REVERSED SUBSTITUENT EFFECT IN 5-FLUOROBICYCLO[3.3.3]UNDECANE-1-CARBOXYLICACID

Relative proton transfer enthalpies delta DELTAH0 of sp and ap conform ers of 5-fluorobicyclo[3.3.3]undecane-1-carboxylic acid have been calc ulated by the AM1 method and the results were compared with the predic tion of the electrostatic theory. It is shown that the great reversed substituent effect in the sp conformer (delta DELTAH0 = 32.1 kJ mol-1) is substantially overestimated largely due to sterical Baeyer strain and non-bonded interactions.