DFT-calculated structures based on 1H NMR chemical shifts in solution vs. structures solved by single-crystal X-ray and crystalline-sponge methods: Assessing specific sources of discrepancies

Siskos, Michael G.; Choudhary, M. Iqbal; Gerothanassis, Ioannis P.

doi:10.1016/j.tet.2018.07.038

Cited by 19 publications

(20 citation statements)

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“…The development of quantum chemical methods for calculating NMR chemical shifts has led to a significant number of studies that combine experimental chemical shifts with computations [ 39 , 40 , 41 , 42 ]. Nevertheless, a few examples of organic molecules whose structures have been determined by both computations of NMR chemical shifts in solution and X-ray structures have been published [ 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. Since no X-ray structures of the hydroperoxides of fatty acids have so far been reported, it would be of interest to investigate three-dimensional structures of hydroperoxides of the present work, which are based on the combined use of quantum chemical calculations and 1 H-NMR chemical shifts.…”

Section: Resultsmentioning

confidence: 99%

NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric Endo-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate

et al. 2020

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A combination of selective 1D Total Correlation Spectroscopy (TOCSY) and 1H-13C Heteronuclear Multiple Bond Correlation (HMBC) NMR techniques has been employed for the identification of methyl linolenate primary oxidation products without the need for laborious isolation of the individual compounds. Complex hydroperoxides and diastereomeric endo-hydroperoxides were identified and quantified. Strongly deshielded C–O–O–H 1H-NMR resonances of diastereomeric endo-hydroperoxides in the region of 8.8 to 9.6 ppm were shown to be due to intramolecular hydrogen bonding interactions of the hydroperoxide proton with an oxygen atom of the five-member endo-peroxide ring. These strongly deshielded resonances were utilized as a new method to derive, for the first time, three-dimensional structures with an assignment of pairs of diastereomers in solution with the combined use of 1H-NMR chemical shifts, Density Functional Theory (DFT), and Our N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) calculations.

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Section: Resultsmentioning

confidence: 99%

NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric Endo-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate

et al. 2020

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“…NMR spectral shift enhancement is recognised as a criterion of hydrogen bonding, and many correlations between shifts and different measures of the hydrogen‐bond strength, not only in complexes but also related to intramolecular interactions, have been proposed. Such correlations have been used to infer hydrogen‐bond strengths or distances from spectroscopic data. The question arises as to what measure of the bond strength is appropriate for these correlations.…”

Section: Discussionmentioning

confidence: 99%

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

Lomas

2019

Magnetic Reson in Chemistry

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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 diazacycloalkanes, 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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“…Siskos et al argue that due to their incredible sensitivity to structural parameters and interactions such as hydrogen bonds, calculated chemical shifts can lead to structural information that is of greater accuracy than that obtained by single‐crystal X‐ray studies.…”

Section: Applicationsmentioning

confidence: 99%

Calculating nuclear magnetic resonance chemical shifts in solvated systems

Casabianca

2020

Magnetic Reson in Chemistry

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The nuclear magnetic resonance (NMR) chemical shift is extremely sensitive to molecular geometry, hydrogen bonding, solvent, temperature, pH, and concentration. Calculated magnetic shielding constants, converted to chemical shifts, can be valuable aids in NMR peak assignment and can also give detailed information about molecular geometry and intermolecular effects. Calculating chemical shifts in solution is complicated by the need to include solvent effects and conformational averaging. Here, we review the current state of NMR chemical shift calculations in solution, beginning with an introduction to the theory of calculating magnetic shielding in general, then covering methods for inclusion of solvent effects and conformational averaging, and finally discussing examples of applications using calculated chemical shifts to gain detailed structural information.

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DFT-calculated structures based on 1H NMR chemical shifts in solution vs. structures solved by single-crystal X-ray and crystalline-sponge methods: Assessing specific sources of discrepancies

Cited by 19 publications

References 63 publications

NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric Endo-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate

NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric Endo-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate

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

Calculating nuclear magnetic resonance chemical shifts in solvated systems

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DFT-calculated structures based on 1H NMR chemical shifts in solution vs. structures solved by single-crystal X-ray and crystalline-sponge methods: Assessing specific sources of discrepancies

Cited by 19 publications

References 63 publications

NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric Endo-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate

NMR and Computational Studies as Analytical and High-Resolution Structural Tool for Complex Hydroperoxides and Diastereomeric Endo-Hydroperoxides of Fatty Acids in Solution-Exemplified by Methyl Linolenate

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

Calculating nuclear magnetic resonance chemical shifts in solvated systems

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Product

Resources

About

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