Models for Estimation of Pure n-Alkanes' Thermodynamic Properties as a Function of Carbon Chain Length

Simple predictive relationships for the estimation of pure normal alkanes' thermodynamic properties, like transition temperatures, phase change enthalpies, and heat capacities in the solid or liquid state, are established as a function of carbon atom number nc, by combining our own calorimetric experimental results and a general review of literature data. This study underlines that total and melting enthalpies vary linearly with nc carbon atom number, whatever the parity of nc, while order−disorder transition enthalpies show a quadratic variation and an alternating effect between odd- and even-numbered n-alkanes. Heat capacity variations versus temperature and the carbon chain length were represented by a model of group contributions for the liquid phase and by an expression derived from Einstein's model for the solid state.