All acyclic hydrocarbons: formula periodic table and property overlap plots via chemical combinatorics

Abstract

It is sought to extend the characterization of isomer classes by using combinatoric techniques long used for isomer enumerations. To this end a general family of isomers (which is challenging to deal with even at the level of conventional enumeration) is considered, namely that of all acyclic hydrocarbons C_nH_2m with classical valence structures. This set of hydrocarbons is partitioned into structural-isomer classes, and these in turn are presented in the form of a ‘‘ formula periodic table’’ with n and m identifying rows and columns, respectively. Then various isomer-class-averaged characteristics (beyond isomer enumerations) are sought to be entered into the associated positions in this periodic table. Such characteristics include heat of formation, magnetic susceptibility and index of refraction, each of which may be estimated via substructural ‘‘cluster expansion’’. These cluster-expansion-estimated property averages as well as associated standard deviations are developed by way of a generating-function chemical combinatorics for isomers of up to n=25 carbons and 2m=52 hydrogens. These results then are incorporated in property ‘‘ overlap plots’’ to reveal overall isomer-class property trends in the periodic table for this set of ≈10¹³ structural isomers distributed over ≈360 isomer classes.