Relationships between NMR shifts and interaction energies in biphenyls, alkanes, aza-alkanes, and oxa-alkanes with X─H… H─Y and X─H… Z (X, Y = C or N; Z = N or O) hydrogen bonding
© 2019 John Wiley & Sons, Ltd.
| Veröffentlicht in: | Magnetic resonance in chemistry : MRC. - 1985. - 57(2019), 12 vom: 19. Dez., Seite 1121-1135 |
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| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2019
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| Zugriff auf das übergeordnete Werk: | Magnetic resonance in chemistry : MRC |
| Schlagworte: | Journal Article Research Support, Non-U.S. Gov't IQA NCI NMR shifts QTAIM hydrogen bonding interaction energies |
| Zusammenfassung: | © 2019 John Wiley & Sons, Ltd. Hydrogen-hydrogen C─H… H─C bonding between the bay-area hydrogens in biphenyls, and more generally in congested alkanes, very strained polycyclic alkanes, and cis-2-butene, has been investigated by calculation of proton nuclear magnetic resonance (NMR) shifts and atom-atom interaction energies. Computed NMR shifts for all protons in the biphenyl derivatives correlate very well with experimental data, with zero intercept, unit slope, and a root mean square deviation of 0.06 ppm. For some congested alkanes, there is generally good agreement between computed values for a selected conformer and the experimental data, when it is available. In both cases, the shift of a given proton or pair of protons tends to increase with the corresponding interaction energy. Computed NMR shift differences for methylene protons in polycyclic alkanes, where one is involved in a very short contact ("in") and the other is not ("out"), show a rough correlation with the corresponding C─H… H─C exchange energies. The "in" and "in,in" isomers of selected aza- and diaza-cycloalkanes, respectively, are X─H… H─N hydrogen bonded, whereas the "out" and "in,out" isomers display X─H… N hydrogen bonds (X = C or N). Oxa-alkanes and the "in" isomers of aza-oxa-alkanes are X─H… O hydrogen bonded. There is a very good general correlation, including both N─H… H─Y (Y = C or N) and N─H… Z (Z = N or O) interactions, for NH proton shifts against the exchange energy. For "in" CH protons, the data for the different C─H… H─Y and C─H… Z interactions are much more dispersed and the overall shift/exchange energy correlation is less satisfactory |
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| Beschreibung: | Date Completed 21.11.2019 Date Revised 08.01.2020 published: Print-Electronic Citation Status PubMed-not-MEDLINE |
| ISSN: | 1097-458X |
| DOI: | 10.1002/mrc.4900 |