The Importance of Inter- and Intramolecular van der Waals Interactions in Organic Reactions: the Dimerization of Anthracene Revisited

摘要

The van der Waals (also called dispersive) interactions between atoms and molecules play an important role in many chemical systems. They are delicately balanced with electrostatic and exchange/repulsion interactions[1] and together they control, for example, the structures of DNA and proteins, the packing of crystals, the formation of aggregates, host-guest systems, and the orientation of molecules on surfaces or in molecular films.[2] It is generally believed that van der Waals effects are of major importance only for intermolecular situations (for example, weakly bonded complexes), although there are theoretical indications that, for example, protein folding is also significantly influenced by intramolecular van der Waals interactions.[3] It is shown herein for the first time that these effects are also of particular importance for the accurate description of the thermodynamics of normal chemical reactions. Furthermore, it will be shown how and why actual implementations of Kohn-Sham density functional theory (DFT)[4] yield a seemingly right answer for the wrong reason.