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Assessment of the Presence and Strength of H-Bonds by Means of Corrected NMR

The downfield shift of the NMR signal of the bridging proton in a H-bond (HB) is composed of two elements. The formation of the HB causes charge transfer and polarization that lead to a deshielding. A second factor is the mere presence of the proton-accepting group, whose electron density and respon...

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Autor principal: Scheiner, Steve
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6274571/
https://www.ncbi.nlm.nih.gov/pubmed/27801801
http://dx.doi.org/10.3390/molecules21111426
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author Scheiner, Steve
author_facet Scheiner, Steve
author_sort Scheiner, Steve
collection PubMed
description The downfield shift of the NMR signal of the bridging proton in a H-bond (HB) is composed of two elements. The formation of the HB causes charge transfer and polarization that lead to a deshielding. A second factor is the mere presence of the proton-accepting group, whose electron density and response to an external magnetic field induce effects at the position of the bridging proton, exclusive of any H-bonding phenomenon. This second positional shielding must be subtracted from the full observed shift in order to assess the deshielding of the proton caused purely by HB formation. This concept is applied to a number of H-bonded systems, both intramolecular and intermolecular. When the positional shielding is removed, the remaining chemical shift is in much better coincidence with other measures of HB strength.
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spelling pubmed-62745712018-12-28 Assessment of the Presence and Strength of H-Bonds by Means of Corrected NMR Scheiner, Steve Molecules Article The downfield shift of the NMR signal of the bridging proton in a H-bond (HB) is composed of two elements. The formation of the HB causes charge transfer and polarization that lead to a deshielding. A second factor is the mere presence of the proton-accepting group, whose electron density and response to an external magnetic field induce effects at the position of the bridging proton, exclusive of any H-bonding phenomenon. This second positional shielding must be subtracted from the full observed shift in order to assess the deshielding of the proton caused purely by HB formation. This concept is applied to a number of H-bonded systems, both intramolecular and intermolecular. When the positional shielding is removed, the remaining chemical shift is in much better coincidence with other measures of HB strength. MDPI 2016-10-27 /pmc/articles/PMC6274571/ /pubmed/27801801 http://dx.doi.org/10.3390/molecules21111426 Text en © 2016 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Scheiner, Steve
Assessment of the Presence and Strength of H-Bonds by Means of Corrected NMR
title Assessment of the Presence and Strength of H-Bonds by Means of Corrected NMR
title_full Assessment of the Presence and Strength of H-Bonds by Means of Corrected NMR
title_fullStr Assessment of the Presence and Strength of H-Bonds by Means of Corrected NMR
title_full_unstemmed Assessment of the Presence and Strength of H-Bonds by Means of Corrected NMR
title_short Assessment of the Presence and Strength of H-Bonds by Means of Corrected NMR
title_sort assessment of the presence and strength of h-bonds by means of corrected nmr
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6274571/
https://www.ncbi.nlm.nih.gov/pubmed/27801801
http://dx.doi.org/10.3390/molecules21111426
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