Defining new Benson groups for use in thermodynamic property estimation software

Group contribution methods provide a simple, safe and economical way to estimate thermodynamic properties for a wide variety of pure compounds and mixtures. Experimental determination of these properties require significantly more time and money than are usually available. CHETAH(TM), a thermodynamic property estimation software package, employs Benson's method, a well known second order group contribution method used to estimate enthalpy of formation, entropy and heat capacity. The expansion of this database is crucial in allowing the analysis of a larger variety of compounds and the analysis of new compounds. Experimental data are used to back calculate unknown groups of interest. When the experimental literature is exhausted, a new approach using computational chemistry, specifically the Gaussian 09 program is utilized containing the G4(MP2) method of enthalpy calculation, to allow the computation of previously elusive groups.