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Proving and Probing the Presence of the Elusive C−H⋅⋅⋅O Hydrogen Bond in Liquid Solutions at Room Temperature
Author(s) -
Galle Kankanamge Susith R.,
Ma Jianbo,
Mackin Robert T.,
Leonik Fedra M.,
Taylor Carol M.,
Rubtsov Igor V.,
Kuroda Daniel G.
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202006210
Subject(s) - chemistry , hydrogen bond , amide , solvation , chloroform , solvation shell , molecule , hydrogen atom , enthalpy , ab initio , hydrogen , crystallography , computational chemistry , group (periodic table) , organic chemistry , thermodynamics , physics
Abstract Hydrogen bonds (H bonds) play a major role in defining the structure and properties of many substances, as well as phenomena and processes. Traditional H bonds are ubiquitous in nature, yet the demonstration of weak H bonds that occur between a highly polarized C−H group and an electron‐rich oxygen atom, has proven elusive. Detailed here are linear and nonlinear IR spectroscopy experiments that reveal the presence of H bonds between the chloroform C−H group and an amide carbonyl oxygen atom in solution at room temperature. Evidence is provided for an amide solvation shell featuring two clearly distinguishable chloroform arrangements that undergo chemical exchange with a time scale of about 2 ps. Furthermore, the enthalpy of breaking the hydrogen bond is found to be 6–20 kJ mol −1 . Ab‐initio computations support the findings of two distinct solvation shells formed by three chloroform molecules, where one thermally undergoes hydrogen‐bond making and breaking.