Aromatic molecular zones and fragments
Laszlo Tarko · ARKIVOC · 2008
An edge on the weighted molecular graph is aromatic if the bond order B value is within [α, β] range.A certain "non-conjugated topological path" includes minimum two adjacent "single" edges (B < α).The topological paths that are not "non-conjugated" are "conjugated topological paths".An aromatic zone is a collection of contiguous aromatic edges.An aromatic fragment is a topological path within aromatic zone.The proposed aromaticity formula measures the aromaticity of zones and any "conjugated paths" via two variables that gauge deviations of bond orders from a reference value and of atom hybridization from sp 2 character.The aromaticity of "non-conjugated paths" is, conventionally, null.The analysis of organic/inorganic molecules, ions and radicals, including those having cyclic, non-cyclic, planar and non-planar geometries, uses a unique set of parameters.The larger the deviation from Hückel rules, the smaller (even negative) is the computed aromaticity value.The paper presents a few non-aromatic Hückel and aromatic non-Hückel structures.After geometry optimization by PM6 method, one can compute the value of some aromaticity molecular descriptors, useful in QSPR computations.The paper includes a list of some descriptors that are measurements of the aromaticity of zones and aromatic "conjugated topological paths".