Perturbating intramolecular hydrogen bonds through substituent effects or non‐covalent interactions

Abstract

An analysis of the effects induced by F, Cl, and Br‐substituents at the α‐position of both, the hydroxyl or the amino group for a series of amino‐alcohols, HOCH2(CH2)nCH2NH2 (n = 0–5) on the strength and characteristics of their OH∙∙∙N or NH∙∙∙O intramolecular hydrogen bonds (IMHBs) was carried out through the use of high‐level G4 ab initio calculations. For the parent unsubstituted amino‐alcohols, it is found that the strength of the OH∙∙∙N IMHB goes through a maximum for n = 2, as revealed by the use of appropriate isodesmic reactions, natural bond orbital (NBO) analysis and atoms in molecules (AIM), and non‐covalent interaction (NCI) procedures. The corresponding infrared (IR) spectra also reflect the same trends. When the α‐position to the hydroxyl group is substituted by halogen atoms, the OH∙∙∙N IMHB significantly reinforces following the trend H < F < Cl