326
Appendix
These ij
H considerations show that with respect to atomic orbital overlap, a
pair of standard and “long-bond” structures (i.e. structures (1) and (3), or (2) and
(3)) are better suited for resonance than are the pair of standard structures (1) and
(2), i.e. the “long-bond” structure (3) helps the standard structures (1) and (2) to
interact by functioning as a “bridge” between them. One may envisage the
conversion of structure (1) into (2) to occur via structure (3), by transferring a Y
electron of structure (1) into the A atomic orbital to afford structure (3), and then
the transfer of an A electron of structure (3) into the B atomic orbital to obtain
structure (2), i.e. the “long-bond” structure forms a connecting link between the
standard structures.
References
1. R.D. Harcourt, J. Mol. Struct., 9, 221 (1971); 12, 351 (1972).
2. J.A. Pople, Trans. Farad. Soc., 49, 1375 (1953).
3. R.D. Harcourt, Aust. J. Chem., 31, 1635 (1978).