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Lack of resonance assistance in a classical intramolecular hydrogen bond: An exploration from quantum theory of atoms‐in‐molecules perspective
Author(s) -
Paul Bijan K.
Publication year - 2019
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3999
Subject(s) - atoms in molecules , chemistry , natural bond orbital , intramolecular force , hyperconjugation , density functional theory , hydrogen bond , computational chemistry , lone pair , antibonding molecular orbital , aromaticity , context (archaeology) , molecular orbital diagram , molecule , chemical physics , valence bond theory , atomic orbital , molecular orbital , electron , stereochemistry , quantum mechanics , physics , organic chemistry , paleontology , biology
A computational investigation has been performed to characterize the intramolecular hydrogen bond (IMHB) interaction in 7‐hydroxy‐2,3‐dihydro‐1 H ‐inden‐1‐one (7H1I). The results of natural bond orbital (NBO) analysis describe the formation of the IMHB in 7H1I in terms of hyperconjugative charge transfer from the lone electron pair of the acceptor oxygen atom (O a ) to the σ* antibonding orbital of the O d ―H 1 proton donating bond. However, the key motivation of the present work rests on characterization of the IMHB interaction by calculation of electron density (ρ c ), its Laplacian (∇ 2 ρ c ), and electron energy density parameters at the bond critical point (BCP) based on the quantum theory of atoms‐in‐molecules (QTAIM). The topological parameters reveal the intriguing result of the lack of resonance assistance in the IMHB of 7H1I despite the presence of an apparently suitable route for the same, contrary to its aromatic (salicylic acid) and nonaromatic ((Z)‐3‐hydroxyacrylaldehyde) analogues. This inference is further supported by an analysis of the aromaticity of the conjoined benzene nucleus. The predominance of hyperconjugation as compared with rehybridization underlying the formation of IMHB in 7H1I is also argued in this context.