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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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Formato: | Online Artículo Texto |
Lenguaje: | English |
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MDPI
2016
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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. |
format | Online Article Text |
id | pubmed-6274571 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2016 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
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 |
work_keys_str_mv | AT scheinersteve assessmentofthepresenceandstrengthofhbondsbymeansofcorrectednmr |