This Small Business Innovation Research Phase I project will lead to a new thermochemical method, "Jaguar 2" (J2), and new software that will demonstrate that the J2 method yields accurate thermochemical data at a low computational cost. Schrodinger, Inc. will develop and refine quantum chemical techniques to improve the accuracy of the J2 terms, and will experiment with different quantum chemical methods and parameter functional forms within the basic J2 model. Schrodinger has previously developed limited correlation schemes (in which different types and basis sets can be used for different regions), and these will be employed and tested within the J2 model. The J2 software will also include automated methods to improve treatment of transition-metal-containing systems and other difficult cases. With this Phase I software, expert users will be able to calculate highly accurate transition states, heats of formation, dissociation energies, and pKa's. Schrodinger will test the performance of the method on these properties for a variety of systems, including some organometallic cases. Accurate J2 thermochemical software that allowed routine calculation of thermochemical properties for large molecules would lead to rapid advances in many areas of chemistry, from catalysis to drug binding. The model's ability to help predict reaction barriers, reaction rates, relative bond strengths, and other critical information will lead to an enormous market among both experimental and computational chemists.