Computational <sup>1</sup>H NMR: Part 1. Theoretical background

Krivdin, Leonid B.

doi:10.1002/mrc.4873

Cited by 56 publications

(53 citation statements)

References 163 publications

(246 reference statements)

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“…In addition to the changes of the 31 P{ 1 H} NMR shift, the decrease in the 1 J PC coupling constant in 1‐M (59–72 Hz) compared to ylide 1‐H (135 Hz) was characteristic of the successful α‐metalation. This decrease can be explained by the higher p‐character of the P−C linkage due to the increase of s‐electron density at the ylidic carbon atom to stabilize the two lone pairs of electrons …”

Section: Resultsmentioning

confidence: 99%

Isolation of the Metalated Ylides [Ph₃P−C−CN]M (M=Li, Na, K): Influence of the Metal Ion on the Structure and Bonding Situation

Schwarz

Scharf

Scherpf

et al. 2019

Chemistry A European J

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The isolation and structural characterization of the cyanido‐substituted metalated ylides [Ph 3 P−C−CN]M ( 1‐M ; M=Li, Na, K) are reported with lithium, sodium, and potassium as metal cations. In the solid‐state, most different aggregates could be determined depending on the metal and additional Lewis bases. The crown‐ether complexes of sodium ( 1‐Na ) and potassium ( 1‐K ) exhibited different structures, with sodium preferring coordination to the nitrogen end, whereas potassium binds in an unusual η 2 ‐coordination mode to the two central carbon atoms. The formation of the yldiide was accompanied by structural changes leading to shorter C−C and longer C−N bonds. This could be attributed to the delocalization of the free electron pairs at the carbon atom into the antibonding orbitals of the CN moiety, which was confirmed by IR spectroscopy and computational studies. Detailed density functional theory calculations show that the changes in the structure and the bonding situation were most pronounced in the lithium compounds due to the higher covalency.

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Section: Resultsmentioning

confidence: 99%

Isolation of the Metalated Ylides [Ph₃P−C−CN]M (M=Li, Na, K): Influence of the Metal Ion on the Structure and Bonding Situation

Schwarz

Scharf

Scherpf

et al. 2019

Chemistry A European J

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“…Nuclear magnetic resonance (NMR) spectroscopy is probably the most important experimental technique for identification and structure determination of both organic and inorganic compounds in solution. Nowadays, measurements of NMR spectra are often accompanied by calculations of chemical shifts and indirect nuclear spin–spin coupling constants, the two parameters determining a solution or gas phase NMR spectrum . In particular, the coupling constants can provide important information on, for example, the stereochemistry of compounds, tautomer equilibria, nonbonded interactions, or potentially even chiral discrimination …”

Section: Introductionmentioning

confidence: 99%

RPA(D) and HRPA(D): Two new models for calculations of NMR indirect nuclear spin–spin coupling constants

et al. 2018

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In this article, the RPA(D) and HRPA(D) models for the calculation of linear response functions are presented. The performance of the new RPA(D) and HRPA(D) models is compared to the performance of the established RPA, HRPA, and SOPPA models in calculations of indirect nuclear spin–spin coupling constants using the CCSD model as a reference. The doubles correction offers a significant improvement on both the RPA and HRPA models; however, the improvement is more dramatic in the case of the RPA model. For all coupling types investigated in this study, the results obtained using the HRPA(D) model are comparable in accuracy to those given by the SOPPA model, while requiring between 30% and 90% of the calculation time needed for SOPPA. The RPA(D) model, while of slightly lower accuracy compared to the CCSD model than HRPA(D), offered calculation times of only approximately 25% of those required for SOPPA for all the investigated molecules. © 2018 Wiley Periodicals, Inc.

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“…Other J‐couplings, including 1 J CH , 2 J CC , 2 J CH , 3 J CH , also share this sensitivity to structure . The less frequently measured 1 J CC coupling also provides a valuable metric for evaluating structure . In this study, 1 J CC coupling is exclusively emphasized because it directly provides 13 C─ 13 C connectivity in organic structures.…”

Section: Introductionmentioning

confidence: 96%

“…Another important contributor to 1 J CC couplings is the presence of adjacent heteroatoms where the heteroatom electronegativity and lone electron pair orientation have been correlated with the magnitude to the 1 J CC coupling. Ring conformation, ring strain, and percent s‐character in a given C─C bond have also been experimentally and theoretically shown to influence 1 J CC couplings.…”

Section: Introductionmentioning

confidence: 99%

“…Theoretical methods from calculating 1 J CC values have also been developed using various approaches . Recent theoretical work often relies upon the second‐order polarization propagator approximation technique or density functional theory (DFT) computations that employ the EPR‐III basis set . The EPR‐III basis, although originally developed to predict hyperfine coupling constants in electron paramagnetic resonance, has also been found to accurately reproduce 1 J CC couplings .…”

Section: Introductionmentioning

confidence: 99%

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Evaluating the accuracy of theoretical one‐bond ¹³C─¹³C scalar couplings and their ability to predict structure in a natural product

Powell

Valenti

Bobnar

et al. 2017

Magnetic Reson in Chemistry

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This study explores the feasibility of using a combination of experimental and theoretical 1-bond C─ C scalar couplings ( J ) to establish structure in organic compounds, including unknowns. Historically, J and J studies have emphasized 2 and 3-bond couplings, yet J couplings exhibit significantly larger variations. Moreover, recent improvements in experimental measurement and data processing methods have made J data more available. Herein, an approach is evaluated in which a collection of theoretical structures is created from a partial nuclear magnetic resonance structural characterization. Computed J values are compared to experimental data to identify candidates giving the best agreement. This process requires knowledge of the error in theoretical methods, thus the B3LYP, B3PW91, and PBE0 functionals are evaluated by comparing to 27 experimental values from INADEQUATE. Respective errors of ±1.2, ±3.8, and ±2.3 Hz are observed. An initial test of this methodology involves the natural product 5-methylmellein. In this case, only a single candidate matches experimental data with high statistical confidence. This analysis establishes the intramolecular hydrogen-bonding arrangement, ring heteroatom identity, and conformation at one position. This approach is then extended to hydroheptelidic acid, a natural product not fully characterized in prior studies. The experimental/theoretical approach proposed herein identifies a single best-fit structure from among 26 candidates and establishes, for the first time, 1 configuration and 3 conformations to complete the characterization. These results suggest that accurate and complete structural characterizations of many moderately sized organic structures (<800 Da) may be possible using only J data.

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Computational ¹H NMR: Part 1. Theoretical background

Cited by 56 publications

References 163 publications

Isolation of the Metalated Ylides [Ph₃P−C−CN]M (M=Li, Na, K): Influence of the Metal Ion on the Structure and Bonding Situation

Isolation of the Metalated Ylides [Ph₃P−C−CN]M (M=Li, Na, K): Influence of the Metal Ion on the Structure and Bonding Situation

RPA(D) and HRPA(D): Two new models for calculations of NMR indirect nuclear spin–spin coupling constants

Evaluating the accuracy of theoretical one‐bond ¹³C─¹³C scalar couplings and their ability to predict structure in a natural product

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Computational 1H NMR: Part 1. Theoretical background

Cited by 56 publications

References 163 publications

Isolation of the Metalated Ylides [Ph3P−C−CN]M (M=Li, Na, K): Influence of the Metal Ion on the Structure and Bonding Situation

Isolation of the Metalated Ylides [Ph3P−C−CN]M (M=Li, Na, K): Influence of the Metal Ion on the Structure and Bonding Situation

RPA(D) and HRPA(D): Two new models for calculations of NMR indirect nuclear spin–spin coupling constants

Evaluating the accuracy of theoretical one‐bond 13C─13C scalar couplings and their ability to predict structure in a natural product

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Computational ¹H NMR: Part 1. Theoretical background

Isolation of the Metalated Ylides [Ph₃P−C−CN]M (M=Li, Na, K): Influence of the Metal Ion on the Structure and Bonding Situation

Isolation of the Metalated Ylides [Ph₃P−C−CN]M (M=Li, Na, K): Influence of the Metal Ion on the Structure and Bonding Situation

Evaluating the accuracy of theoretical one‐bond ¹³C─¹³C scalar couplings and their ability to predict structure in a natural product