The CH/π hydrogen bond in chemistry. Conformation, supramolecules, optical resolution and interactions involving carbohydrates

Abstract

The CH/π hydrogen bond is an attractive molecular force occurring between a soft acid and a soft base. Contribution from the dispersion energy is important in typical cases where aliphatic or aromatic CH groups are involved. Coulombic energy is of minor importance as compared to the other weak hydrogen bonds. The hydrogen bond nature of this force, however, has been confirmed by AIM analyses. The dual characteristic of the CH/π hydrogen bond is the basis for ubiquitous existence of this force in various fields of chemistry. A salient feature is that the CH/π hydrogen bond works cooperatively. Another significant point is that it works in nonpolar as well as polar, protic solvents such as water. The interaction energy depends on the nature of the molecular fragments, CH as well as π-groups: the stronger the proton donating ability of the CH group, the larger the stabilizing effect. This Perspective focuses on the consequence of this molecular force in the conformation of organic compounds and supramolecular chemistry. Implication of the CH/π hydrogen bond extends to the specificity of molecular recognition or selectivity in organic reactions, polymer science, surface phenomena and interactions involving proteins. Many problems, unsettled to date, will become clearer in the light of the CH/π paradigm.

Quantum Mechanics/Molecular Mechanics Insights into the Enantioselectivity of the O-Acetylation of (R,S)-Propranolol Catalyzed by Candida antarctica Lipase B

“…This type of interaction is also present between the isopropylamine side chain of propranolol and the residue Trp104 in the medium pocket of CalB, involving the six-membered ring of this residue, in agreement with its higher propensity to form CH-π interactions compared with the five-member ring [4]. As the strength of a CH-π interaction depends on its distance and directionality (the stronger the interaction, the stronger the trend to linearity) [5], the stabilization of each TI-2 in binding mode I is expected to depend strongly on the orientation of the side chains of propranolol in the binding pocket, especially that of its naphthyl group due to its bulky size and its π-donor character. Therefore these CH-π interactions are expected to play an important role in the stabilization of the corresponding transition states (TSs) and thus in the enantioselectivity of the reaction.…”

Bicomponent Supramolecular Architectures at the Vacuum–Solid Interface

“…87 Additionally, a particular class of interaction, usually classified as a weak H-bond and a type of π interaction, is the CH-π interaction. 88,89,90 It consists of the interaction between a CH bond and a orbital belonging to an aromatic molecule. This interaction exhibits some directional character, which favors linear self-assembled structures.…”

RCH3···O Interactions in Biological Systems: Are They Trifurcated H-Bonds or Noncovalent Carbon Bonds?

“…The weakest H-bonding interactions are established between weakly polarized D-H bonds (e.g., aliphatic CH) and mildly electron-rich H-acceptor moieties (e.g., alkene π-electrons) [21][22][23]. While a single interaction is energetically insignificant, when several weak H-bonds coexist they can stabilize protein structures [24][25][26] and contribute to the binding of proteins to carbohydrates [27][28][29][30][31]. Apart from this weak bonding interaction, recent theoretical explorations have suggested that pnicogen and tetrel atoms in their sp 3 hybridized form can act as electron poor entities suitable to accommodate an electron-rich guest [16,[32][33][34][35][36][37].…”