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Ukhanev SA, Fedorov SV, Rusakov YY, Rusakova IL, Krivdin LB. Fluorine spin-spin coupling constants of pentafluorobenzene revisited at the ab initio correlated levels. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2022; 60:901-914. [PMID: 35470458 DOI: 10.1002/mrc.5276] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 04/22/2022] [Accepted: 04/22/2022] [Indexed: 06/14/2023]
Abstract
All possible spin-spin coupling constants, 19 F-19 F, 19 F-13 C, and 19 F-1 H, of pentafluorobenzene were calculated at five different levels of theory, HF, DFT, SOPPA (CCSD), CCSD, and the SOPPA (CCSD)-based composite scheme with taking into account solvent, vibrational, relativistic, and correlation corrections. Most corrections were next to negligible for the long-range couplings but quite essential for the one-bond carbon-fluorine coupling constants. Hartree-Fock calculations were found to be entirely unreliable, while DFT results were comparable in accuracy with the data obtained using the wave function-based methods.
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Affiliation(s)
- Stepan A Ukhanev
- A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
| | - Sergei V Fedorov
- A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
| | - Yuriy Y Rusakov
- A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
| | - Irina L Rusakova
- A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
| | - Leonid B Krivdin
- A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia
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Kaseman DC, Malone MW, Tondreau A, Espy MA, Williams RF. Quantitation of Nuclear Magnetic Resonance Spectra at Earth's Magnetic Field. Anal Chem 2021; 93:15349-15357. [PMID: 34747610 DOI: 10.1021/acs.analchem.1c02910] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The inherently quantitative nature of nuclear magnetic resonance (NMR) spectroscopy is one of the most attractive aspects of this analytical technique. Quantitative NMR analyses have typically been limited to high-field (>1 T) applications. The aspects for quantitation at low magnetic fields (<1 mT) have not been thoroughly investigated and are shown to be impacted by the complex signatures that arise at these fields from strong heteronuclear J-couplings. This study investigates quantitation at Earth's magnetic field (∼50 μT) for a variety of samples in strongly, weakly, and uncoupled spin systems. To achieve accurate results in this regime, the instrumentation, experimental acquisition, processing, and theoretical aspects must be considered and reconciled. Of particular note is the constant field nuclear receptivity equation, which has been re-derived in this study to account for strong coupling and quality factor effects. The results demonstrate that the quantitation of homonuclear molecular groups, determination of heteronuclear pseudoempirical formulas, and mixture analysis are all feasible at Earth's magnetic field in a greatly simplified experimental system.
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Affiliation(s)
- Derrick C Kaseman
- Biome and Bioenergy Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Michael W Malone
- Quantum Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Aaron Tondreau
- Inorganic, Isotope, and Actinide Chemistry Group, Los Alamos, New Mexico 87545, United States
| | - Michelle A Espy
- Non-Destructive Testing and Evaluation Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Robert F Williams
- Biome and Bioenergy Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
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Howe PWA. Recent developments in the use of fluorine NMR in synthesis and characterisation. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2020; 118-119:1-9. [PMID: 32883447 DOI: 10.1016/j.pnmrs.2020.02.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 02/14/2020] [Accepted: 02/20/2020] [Indexed: 06/11/2023]
Abstract
A review of developments in fluorine NMR of relevance to synthesis, characterisation and industrial applications of small organic molecules. Developments considered include those in spectrometer technology, computational methods and pulse sequences. The review of 80 references outlines applications in areas of identification, quantitation, mixture analysis, reaction monitoring, environmental studies and fragment-based drug design.
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Affiliation(s)
- Peter W A Howe
- Syngenta, Jealott's Hill Research Centre, Bracknell, Berkshire RG42 6EY, UK.
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Chemical Analysis of Fluorobenzenes via Multinuclear Detection in the Strong Heteronuclear J-Coupling Regime. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10113836] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Chemical analysis via nuclear magnetic resonance (NMR) spectroscopy using permanent magnets, rather than superconducting magnets, is a rapidly developing field. Performing the NMR measurement in the strong heteronuclear J-coupling regime has shown considerable promise for the chemical analysis of small molecules. Typically, the condition for the strong heteronuclear J-coupling regime is satisfied at µT magnetic field strengths and enables high resolution J-coupled spectra (JCS) to be acquired. However, the JCS response to systematic chemical structural changes has largely not been investigated. In this report, we investigate the JCS of C6H6−xFx (x = 0, 1, 2, …, 6) fluorobenzene compounds via simultaneous excitation and detection of 19F and 1H at 51.5 µT. The results demonstrate that JCS are quantitative, and the common NMR observables, including Larmor frequency, heteronuclear and homonuclear J-couplings, relative signs of the J-coupling, chemical shift, and relaxation, are all measurable and are differentiable between molecules at low magnetic fields. The results, corroborated by ab initio calculations, provide new insights into the impact of chemical structure and their corresponding spin systems on JCS. In several instances, the JCS provided more chemical information than traditional high field NMR, demonstrating that JCS can be used for robust chemical analysis.
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Edgar M, Hayward D, Zeinali F, Riaz S, Weaver GW. NMR spectral analysis of strongly second-order 6-, 8-, 9- and 10- spin-systems ( 1 H─ 19 F, 19 F─ 19 F, and 13 C─ 19 F) in perfluorotoluyl- and tetrafluoro-pyridyl-aromatics using the lineshape method ANATOLIA. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2020; 58:170-185. [PMID: 31660627 DOI: 10.1002/mrc.4947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 09/23/2019] [Accepted: 09/23/2019] [Indexed: 06/10/2023]
Abstract
A simple to use nuclear magnetic resonance analysis method has been tested on complex 1 H, 19 F, and 13 C multiplets. This open-source line-shape analysis method analysis of total lineshape (ANATOLIA)1 provides some significant advantages over traditional assign-iterate methods of NMR spectral analysis by avoiding false minima and progressing optimisation to the global minimum. The target molecules are 1-perfluorotol-4-yl-2-perfluorotol-4-yl-oxymethyl-1H-benzimidazole (molecule-I) and 1-tetrafluoropyrid-4-yl-2-tetrafluoropyrid-4-yl-thio-1H-benzimidazole (molecule-II) which were produced as part of a family of fluorinated drug scaffolds prepared for anticancer and antiparasitic screening. Spectra display significant second-order effects with 1 H Δδ = 3.68 and 4.67 Hz for the aromatic hydrogen "triplets", with 19 F 4 JAA' , 4 JBB' , 4 JXX' , and 4 JYY' coupling constants range from +4.8 to -14.0 Hz and for 13 C-isotopomers 19 F Δδ of up to 111.56 Hz. A spin-system of six coupling nuclei (Ha Hb Hc Hd FY FY' ) was analysed in 12 s, a spin-system of nine coupling fluorine nuclei (AA'BB'CCC-YY') was analysed within 2 min, and 10 coupling nuclei (XX'YY'ZZZ-BB'-Hd ) was optimised in 6 min using a laptop computer. ANATOLIA was also robust enough to be able to yield accurate spectral values from inaccurate input values. In both compounds, a fluorine-fluorine coupling constant was identified between the two fluoro-aromatic rings (FBB' and FYY' ) of +4.05 and +4.67 Hz and attributed to a through-space interaction. Ab initio structure optimisations and coupling constant calculations provided useful input data for spectral analysis. A modern 19 F nuclear magnetic resonance spectrum of perfluorotoluene (octafluorotoluene) and analysis from 1975 was used as a test data set to assess ANATOLIA.
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Affiliation(s)
- Mark Edgar
- Department of Chemistry, School of Science, Loughborough University, Loughborough, UK
| | - Dee Hayward
- Department of Chemistry, School of Science, Loughborough University, Loughborough, UK
| | - Fatemeh Zeinali
- Department of Chemistry, School of Science, Loughborough University, Loughborough, UK
| | - Shahzad Riaz
- Department of Chemistry, School of Science, Loughborough University, Loughborough, UK
| | - George W Weaver
- Department of Chemistry, School of Science, Loughborough University, Loughborough, UK
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Fischer M, Schmidtmann M. B(C 6F 5) 3- and HB(C 6F 5) 2-mediated transformations of isothiocyanates. Chem Commun (Camb) 2020; 56:6205-6208. [PMID: 32364554 DOI: 10.1039/d0cc02626c] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
This contribution reports on the reactivity of isothiocyanates towards the boranes B(C6F5)3 and HB(C6F5)2. The reactions of alkyl-substituted isothiocyanates with B(C6F5)3 were found to result in rearrangement reactions to yield stable thiocyanate-B(C6F5)3 adducts. Treatment of isothiocyanates with HB(C6F5)2 leads to 1,2-hydroboration and thus, B,N,C,S heterocycles are formed, which react further under non-inert conditions. Hydrolysis of the hydroboration products leads to a new access to thioformamides.
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Affiliation(s)
- Malte Fischer
- Institute of Chemistry, Carl von Ossietzky University Oldenburg, Carl von Ossietzky Straße 9-11, D-26129 Oldenburg, Germany.
| | - Marc Schmidtmann
- Institute of Chemistry, Carl von Ossietzky University Oldenburg, Carl von Ossietzky Straße 9-11, D-26129 Oldenburg, Germany.
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