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ABSTRACT The interaction energies within noncovalent bonds can be partitioned into electrostatic, induction, and dispersive attractive elements. A set of complexes comprising halogen, chalcogen, pnicogen, and tetrel bonds, are studied by quantum chemical calculations to assess how each of these components can be understood on the basis of properties of the constituent monomers. The variation of the electrostatic term, which accounts for over half of the total attractive energy, can be approximated, but with only modest accuracy, by combination of the maximum and minimum of the electrostatic potential on the two subunits. Induction represents a smaller contribution to the total, but is well connected with the NBO interorbital transfer energy, as opposed to the reciprocal of the HOMO‐LUMO gap which behaves quite differently than IND. Of the various AIM parameters, both the bond critical point density and energy density are closely related to the full interaction energy. 

The ability of the CH group to act as proton donor is now widely accepted, even if the H bonds (HBs), which it forms are typically much weaker than those of the hydroxyl group, particularly for a sp³‐hybridized C. An NH₃nucleophile is allowed to approach both the terminal methyl group and the hydroxyl of n‐butanol, so as to form either a CH··N or OH··N HB. Density functional theory calculations show that the latter is much stronger than the former. However, the strength of the CH··N HB can be amplified and approach much closer to that of OH··N by appropriate placement of suitable electron‐withdrawing and donating substituents on the butanol. The interaction energy of the CH··N HB reaches above 6–8 kcal mol⁻¹in several cases, considerably larger than the prototype HB within the water dimer. 

Although it has the geometric characteristics of a halogen bond, the binding between a square planar metal and a halogen atom rests primarily on transfer from the halogen lone pairs to the metal π-hole. 

A H-bond is not possible if the bridging H bears a substantial negative charge. Only a very weak, marginal, H-bond is possible if its charge borders on neutrality. 

Strong negative charge on the tetravalent apical C of propellane can attract an electrophile, which can then extract charge from the prominent lobe of its C–C bonding orbital, to form a strong noncovalent bond with C as an electron donor. 

The occurrence of these anion⋯anion dimers in the crystal structure are dependent on the presence of counterions as the attraction between two Au(iii) centers is insufficient to override the coulombic repulsion. 

Abstract Both methyl groups and benzene rings are exceedingly common, and they lie near one another in many chemical situations. DFT calculations are used to gauge the strength of the attractive forces between them, and to better understand the phenomena that underlie this attraction. Methane and benzene are taken as the starting point, and substituents of both electron‐withdrawing and donating types are added to each. The interaction energy varies between 1.4 and 5.0 kcal/mol, depending upon the substituents placed on the two groups. The nature of the binding is analyzed via Atoms in Molecules (AIM), Natural Bond Orbital (NBO), Symmetry‐Adapted Perturbation Theory (SAPT), nuclear magnetic resonance (NMR) chemical shifts, and electron density shift diagrams. While there is a sizable electrostatic component, it is dispersion that dominates these interactions, particularly the weaker ones. As such, these interactions cannot be categorized unambiguously as either H‐bonds or tetrel bonds. 

The ability of IR and NMR spectra to distinguish between hydrogen and halogen bonding of haloforms is assessed by quantum chemical calculations. 

Quantum calculations show that replacement of the H-bonds within DNA base pairs by halogen bonds can enhance their binding to one another.