Formula periodic table for acyclic hydrocarbon isomer classes: combinatorially averaged graph invariants

The overall isomer classes of acyclic hydrocarbons CnH2m with classical val ence structures can be presented in the form of a formula "periodic table" with n and m identifying rows and columns, respectively. Such a table may b e used to reflect property trends of isomer classes. A general approach is presented for obtaining isomer-class averages of specified molecular proper ties, and the approach is extended to deal with mean square-deviations, so as to estimate the property overlap between the different isomer classes. H ere the properties considered include graph diameters, molecular branching, counts of bonds of different multiplicities, and counts of sites of differ ent hybridizations. Contour plots in the "periodic table" illustrate overal l property trends for families of up to about 10(12) structural isomers las arise for isomer classes of up to n = 25 carbon atoms). Evidently, an over all view of various property trends of acyclic hydrocarbon isomer classes i s possible.