Prediction of standard absolute entropies for gaseous organic compounds

摘要

To predict the standard absolute entropies of gaseous organic compounds, the variable molecular connectivity index (~(m)(chi)_(k)") and Ring parameter (H), based on the adjacency matrix of molecular graphs, the variable atomic valence connectivity index ((delta)_(i)"), and the numbers of chain (cycle) atom of a molecule (n_(i)~(R)) were proposed. The (delta)_(i)", ~(m)(chi)_(k)" and H are defined as: (delta)_(i)" velence c (Z_(i)~(v)-h_(i)) m_(i) 2.89~(a)/(Z_(i)-Z_(i)~(v) + 0.89)~(a), ~(m)(chi)_(k)" velence sum from i=1 to n_(m) of (PI_(i=1)~(m+1)(delta)_(i)")_(j)~(-y), and H velence (In(1.29 + 0.31 n_(i)~(R)))~(2.4). The optimal values of the parameters c, a, m_(i), and y included in definition of the delta_(i)" and ~(m)(chi)_(k)" can be found by the optimization method. The result shows that the definition of the delta_(i)", for a skeletal atom, expresses both electronic and topological information, and can reflect the different chemical environment of the given atom. A four-parameter model can be constructed from the H and ~(m)(chi)_(k)" by using the best subset regression analysis method and the model could be used to predict the standard absolute entropies of gaseous organic compounds accurately.