Choice of nonlinear regression functions for various physicochemical constants within series of homologues

Abstract The method for searching optimal approximation functions to describe the dependence of various physicochemical constants ( P ) of organic compounds on the number of carbon atoms in the molecules of homologues ( n C ) is considered. This approach is based on the choice of an appropriate function for the second numerical derivatives P ʺ( n C ) of the considered properties followed by its twice integration. The general function for all principal properties—reciprocal boiling points (1/ T b ), refractive indices ( n D 20 ) or relative densities ( d 4 20 ), having limiting values when n C →∞,—is P ʺ( n C )= A ( n C − B ) C ( C