Correlations of critical properties with computed molecular surface areas for 11 homologous series of 118 organic compounds

A simple and convenient method for predicting critical constants (Tc, Pc, and Vc) for members of a homologous series was developed from computed molecular surface areas obtained from a molecular modeling program (CAChe version 3.5). The best linear correlations are obtained when Vc and TcPc0.5 are plotted against computed molecular surface area (SA) and when Tc and Pc are plotted against the natural logarithm of surface area, In SA, for 11 homologous series with a total of 118 organic compounds. The series included n-alkanes, n-alkyl primary amines, n-alkyl primary alcohols, acetate esters, n-alkyl primary thiols, secondary alcohols, n-alkylbenzenes, 2-methylalkanes, perfluoroalkanes, methyl esters, and ethyl esters. For C2C19 n-alkanes, the calculated Tc (K) values agreed well with the literature critical temperatures (R = 1.000) and with other previously described correlations. Similar Tc correlations were found with the other 10 homologous series. The correlation between TcPc0.5 and SA for the 11 homologous series is particularly striking and suggests a strong relationship between molecular surface area and intermolecular attractions.