engleski

Limitations of Pauling Bond Order Concept

It is shown that Kekule structures do not realistically predict the behavior of p-electron properties of those polycyclic hydrocarbons that have many fixed double bonds. This is caused by the fact that such molecules would be destabilized by delocalization. We analyze a group of polycyclic hydrocarbons with a large number of fixed bonds, whose geometry was determined by means of an unrestricted symmetry-broken UB3LYP/6-311G(d, p) DFT method. We put forward a new concept, the unpaired bond order, and show that it is well correlated with bond lengths, but poorly correlated with Pauling bond orders. Hence, in this way we provide a simple test of the validity of the Pauling-bond-order concept for the molecule being considered.

Pauling bond order; bond length

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