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Resonance Energy of Conjugated Hydrocarbons Derived by Cluster Expansion

D. Babić ; Ruđer Bošković Institute, P.O.B. 1016, 41001 Zagreb, Croatia
N. Trinajstić ; Ruđer Bošković Institute, P.O.B. 1016, 41001 Zagreb, Croatia

Puni tekst: engleski pdf 25.318 Kb


str. 881-892

preuzimanja: 254



Resonance energy of conjugated hydrocarbons is considered through the cluster expansion concept. For the first time it is applied in its exact form and fullness. A comparison with previous results, which were obtained by a truncation of the expansion, indicates a high sensitivity of the result to the extent of truncation. The result, which greatly reduces the computation and simplifies implementation, is presented in the paper.
The reference structure is defined in graph-theoretical terms, but the application of the model is not confines to any particular method for electron energy evaluation, o-electrons can be also accounted for. The final expression is parameter free and requires a knowledge of electron energies of the molecule and of its certain acyclic fragments.
The model is examined within the framework of the Hückel jc-electron approximation. The results obtained for a number of molecules show unexpected disagreement with commonly accepted values. However, these results qualitatively agree with the recent results of Shaik et at. by which jr-electron delocalization is interpreted as a generally destabilizing effect.

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