Preface

Siehl, Hans‐Ullrich; Ruasse, Marie-Fran�oise

doi:10.1002/1099-1395(200010)13:10<559::aid-poc313>3.0.co;2-o

Cited by 20 publications

(34 citation statements)

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“…Quantum mechanical calculations of nuclear magnetic resonance (NMR) parameters, such as chemical shifts and coupling constants, have become a very popular tool for synthetic and natural product chemistry for the assignment of stereochemistry within a molecule. Calculations of NMR chemical shifts have been reviewed extensively . These calculations have also been used for the reassignment of incorrectly assigned natural products, as the validation of the proposed structure through gold standard methods like X‐ray crystallography or total synthesis might not be achievable.…”

Section: Introductionmentioning

confidence: 99%

¹H and ¹³C NMR scaling factors for the calculation of chemical shifts in commonly used solvents using density functional theory

2014

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Calculation of NMR chemical shifts and coupling constants using quantum mechanical calculations [density functional theory (DFT)], has become a very popular tool for the determination of conformation and the assignment of stereochemistry within a molecule. We present the scaling factors (linear regression parameters) from 10 DFT methods for 10 commonly used NMR solvents using the same set of reference compounds. The results were compared with the corresponding gas-phase calculations to assess the inclusion of the polarizable continuum model for solvent effects.

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Section: Introductionmentioning

confidence: 99%

¹H and ¹³C NMR scaling factors for the calculation of chemical shifts in commonly used solvents using density functional theory

2014

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“…1. Apart from sharing this feature the compounds are from various classes, such as nitroso (39) and azo-hydrazo (40)(41)(42) compounds, enamines (43)(44)(45), amides (12,46), thioamides (48)(49)(50)(51), carboxylic acids (38),ˇ-keto esters (10,11,13),ˇ-diketones (1-6, 14, 15),˛-acetyl-ˇ-diketones (7-9, 37, 47),ˇ-thioxoketones (52)(53)(54), hydroxyanthraquinones (16-18, 21, 22), hydroxynaphthoquinones (19,20,23,24), o-hydroxy aromatic ketones (25-30, 32-36, 37, 55) and esters (31). This range of compounds covers intramolecular hydrogen-bonded systems with oxygen, nitrogen and sulfur in the donors and acceptor functions.…”

Section: Introductionmentioning

confidence: 99%

Primary tritium and deuterium isotope effects on chemical shifts of compounds having an intramolecular hydrogen bond

Bolvig¹,

Hansen²,

Morimoto³

et al. 2000

Magn. Reson. Chem.

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The primary deuterium and tritium isotope effects, δ(XH) − δ(XD/T), were measured for 55 compounds having one or more intramolecular hydrogen bonds. The primary isotope effects were measured at various temperatures. For compounds displaying tautomerism the primary isotope effects are found to have contributions from both intrinsic and equilibrium isotope effects. The primary tritium isotope effect, PΔ(1H,3H), and the primary deuterium isotope effect, PΔ (1H,2H), are shown to be related by This finding is valid for both tautomeric compounds and compounds with localized hydrogen bonds. Large negative primary tritium and deuterium isotope effects were observed for compounds displaying tautomerism and having sulfur as donor or acceptor. These isotope effects show a strong temperature dependence, which is related to the change in equilibrium due to isotope substitution. For the compounds with localized hydrogen bonds, the primary deuterium and tritium isotope effects correlated with the two bond deuterium isotope effect on 13C chemical shifts. The primary deuterium and tritium isotope effects are therefore a measure of the hydrogen bond strength for compounds with localized hydrogen bonds. Copyright © 2000 John Wiley & Sons, Ltd.

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“…The method was developed by Martin Saunders and, as its name suggests, uses equilibrium isotope effects to alter dynamically equivalent NMR chemical shifts. It is a general method that has been reviewed in the literature and has been applied to chemical systems in which symmetry is in doubt [15]; examples include molecules that rapidly interconvert asymmetric isomers via pericyclic reactions [16], bond rotations [17], and proton transfers [18]. In the following, I provide a brief description of the method using symmetric and asymmetric 2-d 3 …”

Section: Methodsmentioning

confidence: 99%

The structure of halonium ions in superacidic solutions

Ohta

2013

Pure and Applied Chemistry

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Isotopic perturbation of equilibrium was applied to 1,2-bridged halonium ions to determine whether they exist as single symmetric structures or as a rapid equilibrium of asymmetric structures. The observed deuterium isotope shifts are qualitatively and quantitatively consistent with the presence of intrinsic and equilibrium isotope shifts. The presence of equilibrium shifts suggests that these ions exist as a rapid equilibrium of asymmetric structures. Though the asymmetric structures were initially ascribed to β-halocarbenium ions, subsequent computational data suggest that 1,2-bridged halonium ions react with sulfur dioxide (SO 2 ), the experimental solvent. Our current hypothesis is that the equilibrium isotope shifts result from rapid labile addition of SO 2 to the halonium ions. Other hypotheses have been invoked to explain the results and are considered in the context of the available data.

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Preface

Cited by 20 publications

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¹H and ¹³C NMR scaling factors for the calculation of chemical shifts in commonly used solvents using density functional theory

¹H and ¹³C NMR scaling factors for the calculation of chemical shifts in commonly used solvents using density functional theory

Primary tritium and deuterium isotope effects on chemical shifts of compounds having an intramolecular hydrogen bond

The structure of halonium ions in superacidic solutions

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Preface

Cited by 20 publications

References 0 publications

1H and 13C NMR scaling factors for the calculation of chemical shifts in commonly used solvents using density functional theory

1H and 13C NMR scaling factors for the calculation of chemical shifts in commonly used solvents using density functional theory

Primary tritium and deuterium isotope effects on chemical shifts of compounds having an intramolecular hydrogen bond

The structure of halonium ions in superacidic solutions

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¹H and ¹³C NMR scaling factors for the calculation of chemical shifts in commonly used solvents using density functional theory

¹H and ¹³C NMR scaling factors for the calculation of chemical shifts in commonly used solvents using density functional theory