Abstract: Connectivity indices of 85 alkanes were calculated based on the definition of M. Randic. The properties such as the standard enthalpies of formation, the standard entropies and the standard free energies of formation of these alkanes were correlated with the connectivity indices and the number of carbon atoms. A general equation was proposed as follows; P = a X + bN + c. The thermodynamic properties calculated for both gasous and liquid states of the 85 alkanes are in excellent agreement with the experimental values through regression analysis.