On Electrostatics, Covalency, and Chemical Dashes: Physical Interactions versus Chemical Bonds

Abstract

The increasing availability of real‐space interaction energies between quantum atoms or fragments that provide a chemically intuitive decomposition of intrinsic bond energies into electrostatic and covalent terms [see, for instance, Chem. Eur. J. 2018, 24, 9101] provides evidence for differences between the physicist's concept of interaction and the chemist's concept of a bond. Herein, it is argued that, for the former, all types of interactions are treated equally, whereas, for the latter, only the covalent short‐range interactions have actually been used to build intuition about chemical graphs and chemical bonds. This has led to the bonding role of long‐range Coulombic terms in molecular chemistry being overlooked. Simultaneously, blind consideration of electrostatic terms in chemical bonding parlance may lead to confusion. The relationship between these concepts is examined herein, and some notes of caution on how to merge them are proposed.

A Molecular Electron Density Theory Study of the Chemoselectivity, Regioselectivity, and Diastereofacial Selectivity in the Synthesis of an Anticancer Spiroisoxazoline derived from α-Santonin

“…In order to quantify the nature of these non-covalent O3–H interactions, an IQA energy decomposition analysis [38,47,48] was performed. Due to molecular size restrictions, the IQA analysis was performed at reduced models of TS1 and TS2 (see TS1r and TS2r in Figure S3 in Supplementary Material), whose geometries were not optimized in order to keep the core lactone and nitrile oxide frameworks unvaried.…”

On the Nature of the Positronic Bond

“…It is a well-established fact that e-DI is a measure of the inter-basin electron number fluctuations, revealing the covalency of the bond (in ionic systems or in the case of the inter-molecular interactions, lacking covalency, its value usually diminishes below 0.2). [78,86] The computed inter-basin electronic exchange energy, V xc ee ðH 1 ; H 2 Þ �À 38 kJ mol À 1 ðV xc ee ðH 1 ; H 2 Þ �À 32 kJ mol À 1 in the case of H À 2 2 ), which is an energetic measure of the covalency, [87,88] is also appreciably small compared to those derived from the IQA analysis of classical covalent systems. [84,88,89] Since H À 2 2 is an unbound system without a discernable covalent bond, [49] it seems reasonable to conclude that the origin of bonding in [H À , e + , H À ] cannot be traced in the electronic exchange phenomenon.…”

“…[78,86] The computed inter-basin electronic exchange energy, V xc ee ðH 1 ; H 2 Þ �À 38 kJ mol À 1 ðV xc ee ðH 1 ; H 2 Þ �À 32 kJ mol À 1 in the case of H À 2 2 ), which is an energetic measure of the covalency, [87,88] is also appreciably small compared to those derived from the IQA analysis of classical covalent systems. [84,88,89] Since H À 2 2 is an unbound system without a discernable covalent bond, [49] it seems reasonable to conclude that the origin of bonding in [H À , e + , H À ] cannot be traced in the electronic exchange phenomenon. To proceed further, the remaining energy terms of the extended IQA method which includes all classical coulombic interactions are considered.…”

“…The origin of bonding is traced in this group and is usually attributed to the covalent bonding originating from electron exchange phenomenon while the remaining terms, , , , , are usually conceived collectively as classical coulombic interactions and attributed to the ionic bonding ,. Thus, the inter‐basin interaction is rewritten as follows [Eq.…”

On the Uselessness of Bond Paths Linking Distant Atoms and on the Violation of the Concept of Privileged Exchange Channels

“…In the light of this article, it is necessarily to mention that some have been trying to explain the presence of bond path by referring to the concept of exchange energy. Namely, using several molecular systems and then introducing a very interesting concept of the so‐called privileged exchange channels, Pendás et al .…”