
TY  - JOUR
A1  - Brown, RD 
A1  - Coller, AW 
T1  - A theoretical study of the chemisty of Furan, Phrrole, Benzofuran, Indole, Dibenzofuran, and Carbazole
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1959
VL  - 12
IS  - 2
SP  - 152
EP  - 165
KW  - 
UR  - https://doi.org/10.1071/CH9590152 
N2  - It is shown that it is possible, within the framework of the simple Hückel molecular- orbital method, to account fully for all observations on electrophilic substitution in furan, pyrrole, benzofuran, indole, dibenzofuran, and carbazole, in terms of the &#960;-electron distributions in these compounds. The values of coulomb parameters required to obtain this correlation are physically reasonable and in particular are in agreement with values found independently by a variable electronegativity self-consistent field calculation on pyrrole.   The previously puzzling difference in orientation of substitution in benzofuran and indole is accounted for in the present study in terms of a difference in the auxiliary inductive effects of the two hetero-atoms. It seems possible to attribute this difference ultimately to differences in the CO and CN bond lengths and to differences in the effective nuclear charges for 2p&#960; atomic orbitals on the two hetero-atoms.   Attention is drawn to an &quot; isoprotonic principle &quot; for estimating the value of the primary coulomb parameter of a hetero-atom. (It is probably a special case of a more general principle-that the primary coulomb parameter is predominantly determined by the charge on the core and scarcely depends upon the nature of the nucleus at the centre of the core.)   A spurious Hückel molecular-orbital model for the oxygen heterocycles is noted. It accounts for the chemistry of the heterocycles but represents a physically unsatisfactory view of the electronic properties of oxygen in these compounds. 
ER  -

