Noncovalent Interaction: A Chemical Misnomer That Inhibits Proper Understanding of Hydrogen Bonding, Rotation Barriers, and Other Topics

We discuss the problematic terminology of noncovalent interactions as commonly applied to hydrogen bonds, rotation barriers, steric repulsions, and other stereoelectronic phenomena. Although categorization as noncovalent seems to justify classical-type pedagogical rationalizations, we show that these phenomena are irreducible corollaries of the same orbital-level conceptions of electronic covalency and resonance that govern all chemical bonding phenomena. Retention of such nomenclature is pedagogically misleading in supporting superficial dipole-dipole and related simple, neat, and wrong conceptions as well as perpetuating inappropriate bifurcation of the introductory chemistry curriculum into distinct covalent vs. noncovalent modules. If retained at all, the line of dichotomization between covalent and noncovalent interaction should be re-drawn beyond the range of quantal exchange effects (roughly, at the contact boundary of empirical van der Waals radii) to better unify the pedagogy of molecular and supramolecular bonding phenomena.

Automated summary

This article discusses the problematic use of the term "noncovalent interactions" in relation to hydrogen bonds, rotation barriers, steric repulsions, and other stereoelectronic phenomena. It is argued that these phenomena are consequences of the same orbital-level concepts of electronic covalency and resonance that govern all chemical bonding phenomena. The retention of such terminology is misleading and perpetuates inappropriate division of the introductory chemistry curriculum into separate covalent and noncovalent modules. If retained, the line of distinction between covalent and noncovalent interactions should be redrawn to better unify the pedagogy of molecular and supramolecular bonding phenomena.