Applications of isodesmic‐type reactions for computational thermochemistry

Abstract In computational thermochemistry, “isodesmic‐type” reactions play a significant role for obtaining accurate thermochemical quantities using low‐cost methods that can be applied to large systems. This review touches on some of the examples. For instance, a series of relative bond dissociation energies (BDEs) have been devised to calculate absolute BDEs with near‐chemical‐accuracy (~5 kJ mol−1) using density functional theory (DFT) methods. To facilitate the applicability of isodesmic‐type reactions, the connectivity‐based hierarchy (CBH) has been developed to automate the systematic generation of isodesmic‐type reaction schemes, and applied to large organic and biomolecular systems. The related netCBH scheme yields accurate reaction energies in complex organic reactions, achieving coupled‐cluster quality results at DFT cost. Isodesmic‐type reactions have been used to obtain heats of formation for medium‐sized fullerenes, with uncertainties of ~20 kJ mol−1 up to C180. In comparison, the literature C60 heat of formation has an uncertainty of 100 kJ mol−1. Importantly, it fills the gap in which heats of formation for those larger fullerenes are not available. These studies showcase how isodesmic‐type reactions propel the accuracy of quantum chemistry computations to a level that rivals or even betters modern experimental determinations, particularly for systems that are difficult to study experimentally. This article is categorized under: Structure and Mechanism > Reaction Mechanisms and Catalysis Electronic Structure Theory > Combined QM/MM Methods Theoretical and Physical Chemistry > Thermochemistry