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

A delicate balance between inter- and intramolecular van der Waals effects can significantly influence the thermodynamics of organic reactions. These “weak interactions” are often underestimated but sum up even for the simple example of the dimerization of anthracene to relative effects of about 10–15 kcal mol−1. It is furthermore shown why common density functional theory yields a seemingly right answer for the wrong reason.