The Significance of the Bond Lengths and Bond Orders of Conjugated Unsaturated Organic Molecules. The Role of Hetero-Aromaticity in the Tertiary Structures of DNA

New criteria (based on X-ray crystallographic data) for assessing the presence of delocalization in conjugated π systems reveal that delocalization is not a widespread phenomenon in the ground states of many of these π systems. Instead, these molecules prefer to retain highly localized, independent, π systems. Thus, many explanations of the structural features and reactivities of these unsaturated organic molecules, based on their presumed delocalized ground states, must be critically reviewed. This is especially important for understanding the chemistry and properties of hetero-aromatic molecules