Experimental Determination of the Electrostatic Nature of Carbonyl Hydrogen-Bonding Interactions Using IR-NMR Correlations

Abstract

Hydrogen-bonding plays a fundamental role in the structure, function, and dynamics of various chemical and biological systems. Understanding the physical nature of interactions and the role of electrostatics in hydrogen-bonding has been the focus of several theoretical and computational research. We present an experimental approach involving IR-(13)C NMR correlations to determine the electrostatic nature of carbonyl hydrogen-bonding interactions. This report provides a direct experimental evidence of the classical nature of hydrogen-bonding interaction in carbonyls, independent of any theoretical approximation. These results have important implications in chemistry and biology and can be applied to probe the reaction mechanisms involving carbonyl activation/stabilization by hydrogen bonds using spectroscopic techniques.

Effects of neutral and charged substituents on the infrared carbonyl stretching frequencies in phenyl and alkyl benzoates in DMSO

“…In the IR spectra of phenyl benzoates with ortho substituents in the aroxy part, C 6 H 5 CO 2 C 6 H 4 -X, in the present work in DMSO, only one carbonyl stretching band was detected and splitting of the carbonyl stretching bands was not observed similarly to previous findings in CCl 4 . [1] In phenyl benzoates, the aromatic plane in the phenoxy part is rotated out of the carbonyl plane by nearly 90°, [10,62,78,79] and for ortho derivatives, there is only one conformation possible.…”

Halogen bonding as a key interaction in the self‐assembly of iodinated diphenylalanine peptides

“…As a further confirmation of the strong, simultaneous contribution of hydrogen bond in the solid‐state packing, we focused also on the changes of amide I region (1600‐1700 cm −1 ), associated with the stretching vibration of the carbonyl group. As expected, both dipeptides show a consistent red‐shift of the IR signal, moving from bulk powders to the evaporated solutions of DMSO and water/DMSO (Figure S2‐3), the latter having the amide I peak at lower frequencies; this variation indicates that the electron density associated with the carbonyl oxygen is depleted by the interaction with an electropositive moiety, likely a hydrogen atom.…”

Mechanochemical Synthesis and Structure of the Tetrahydrate and Mesoporous Anhydrous Metforminium(2+)-N,N′-1,4-Phenylenedioxalamic Acid (1:2) Salt: The Role of Hydrogen Bonding and n→π * Charge Assisted Interactions

“…Meanwhile, both COOH and COO − groups appear as one signal slightly shifted by ∼2 ppm to high frequencies compared to the starting H 2 pOXA∙2W. This result is similar to that found in other carbonyls because of hydrogen bonding [ 33 ]. The sp-sp disposition between both oxalyl groups, in relation to the phenyl plane, and the presence of two independent molecules of HpOXA − in the asymmetric unit, as well as hydrogen bonding, have the effect of spreading the CH signals of the benzene ring in the 121–118 ppm range.…”