Two new approaches are presented for the calculation of atom and
bond parameters for heteroatom-containing
molecules used in computing graph theoretic invariants. In the
first approach, the atom and bond weights
are computed on the basis of relative atomic electronegativity, using
carbon as standard. In the second
system, the relative covalent radii are used to compute atom and bond
weights, again with the carbon atom
as standard. The new definition of the atom and bond parameters
leads to a periodic variation versus the
atomic number Z, with a more natural variation when compared
with the parameters defined only by Z.
The two approaches are used to define and compute topological
indices based on graph distance. A
quantitative structure−property relationship study is reported for
boiling points of 185 acyclic compounds
with one or two oxygen or sulfur atoms (devoid of hydrogen bonding), in
terms of four or five molecular
descriptors.
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