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.
Key Questions
1. What is hydrogen bonding?
Hydrogen bonding is a type of chemical interaction that involves a hydrogen atom bonded to a highly electronegative atom such as nitrogen, oxygen, or fluorine. The review argues that hydrogen bonding should be understood as an aspect of orbital-level covalency rather than a distinct "noncovalent" interaction.
2. How do chemical bonds work?
The review emphasizes that all chemical bonding phenomena, including those often labeled as "noncovalent," are governed by the same orbital-level conceptions of electronic covalency and resonance. It argues for a unified understanding of bonding based on quantum mechanical principles.
3. What are intermolecular forces?
Intermolecular forces are interactions between molecules. The review suggests that many of these forces, traditionally classified as "noncovalent," should be reconsidered as aspects of covalent bonding at the orbital level.
4. What is the difference between covalent and noncovalent bonds?
The review challenges the traditional dichotomy between covalent and noncovalent bonds. It argues that phenomena often labeled as "noncovalent" are actually manifestations of the same orbital-level covalency principles that govern all chemical bonding.
5. How should chemistry be taught?
The review advocates for a unified approach to teaching chemical bonding, avoiding the artificial separation of "covalent" and "noncovalent" interactions. It suggests that this would provide a more accurate and comprehensive understanding of chemical phenomena.
