
%0 Journal Article
%A Brown, RD 
%A Heffernan, ML 
%T The 'Variable Electronegativity ' Method. II. Pyrrole
%J Australian Journal of Chemistry
%D 1959/09/01
%V 12
%N 3
%P 319-329
%K 
%R https://doi.org/10.1071/CH9590319
%U https://www.publish.csiro.au/paper/CH9590319 
%X The properties of the &#960;-electron system in pyrrole have been studied by a &quot; variable electronegativity &quot; self-consistent field molecular-orbital method and the results compared with those obtained by the conventional SCF procedure. The &#960;-electron distribution calculated by the conventional SCF procedure cannot be satisfactorily reconciled with the observed dipole moment, but the distribution calculated by the VESCF method leads to a predicted dipole moment in good agreement with observation. Polarization of &#963;-bonds makes a negligible contribution to the dipole moment.Derivation of the coulomb parameters for the simple Hückel molecular-orbital method from the VESCF results is considered and the factors responsible for auxiliary inductive effects are discussed. The &#960;-electron ionization potential and the positions of the lowest excited states of pyrrole have been calculated by the VE method. 
