engleski

On the Benzenoid Character of Polycyclic Conjugated Hydrocarbons

Polycyclic conjugated hydrocarbons have previously been c1assified as aromatic, antiaromatic and non-aromatic depending on the presence of conjugated circuits of type 4n+2, 4n or both, respectively. Here we consider polycyclic conjugated hydrocarbons already c1assified as aromatic and propose to differentiate the degree of benzenoid character within such a c1ass. An index B is proposed which quantitatively measures the resemblance of benzenoid hydrocarbons to benzene. It is based on a partitioning of the molecular resonance energy into a part due to conjugated circuits RI (such as those that occur in benzene) and the remaining contributing conjugated circuits Rn, n not 1.The numerical values for the B-indices of different benzenoid systems fully agree with expectations based on intuitive and qualitative chemical considerations. In particular, the so-called fully benzenoid systems show the greatest similarity to benzene, as measured by the index B, thus vindicating the views of Eric Ciar.

Benzenoid Character ; Polycyclic Conjugated Hydrocarbons

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