OPTIMUM GRAPH-THEORETICAL MODELS FOR ENTHALPIC PROPERTIES OF ALKANES

Simple additive schemes based on graph-theoretical properties of molecular graphs are evaluated for correlating thermodynamic properties of alkanes. The properties considered in this work are DELTA-H(f)-degrees(g), DELTA-H(f)-degrees(1), DELTA-H(atomization), heats of vaporization, and heat capacities of vaporization. The original sources for thermochemical data were checked since some of the past attempts to correlate alkane properties, e.g., DELTA-H(f)-degrees(g), have made use of calculated or interpolated values rather than restricting the analysis to experimental data. The evaluation is conducted using stepwise multilinear regression methodology. The statistical qualities of the final correlative equations are excellent (in all cases but one, squared multiple correlation coefficients > 0.995). In each case, the most successful model equation involves the use of labeled paths of length zero, one, and two as the independent variables. Therefore, each parameter has a simple molecular structure interpretation and can be obtained from the molecular graph by inspection.