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Spectroscopy
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
Since proton nmr examines the hydrogen atoms in a sample, the solvent should not have hydrogen atoms as they will absorb and generate a peak or peaks in the proton nmr that will “swamp out” all signal associated with the sample. Alternatively, all the hydrogen atoms can be replaced by deuterium since deuterium will absorb at a different energy relative to a hydrogen atom. Therefore, typical solvents include CDCl3, d6-acetone, D2O, and d6-DMSO. To reiterate, deuterated solvents are used so they will not contribute signals to the proton nmr that can obscure peaks that are due to the sample of interest. What is a proton nmr spectrum?
Nuclear Magnetic Resonance Spectroscopy
Published in Rui Yang, Analytical Methods for Polymer Characterization, 2018
In solutions, the electron density around nuclei in solute molecules are shielded or deshielded by the surrounding solvent molecules, accordingly changing the chemical shifts. For example, the resonance signals of substances dissolved in aromatic solvents are observed at small chemical shifts as compared with those of substances dissolved in aliphatic solvents. Furthermore, nuclei in solvents may also contribute to the resonance signals in NMR measurement. For avoiding complications, the use of “inert” solvents (e.g., carbon tetrachloride) or deuterated solvents without hydrogen atoms is recommended.
Nuclear Magnetic Resonance
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
The field lock may be viewed as a separate NMR spectrometer within a spectrometer that is tuned to the deuterium resonance frequency. The lock system constantly monitors the deuterium resonance frequency and makes compensatory changes in the Bo magnetic field to keep the resonance frequency constant. To access a deuterium signal, deuterated solvent is typically used in sample preparation. Hence, the spectrometer frequency is kept constant by the application of the field lock that offsets the drift.
A silver(I) coordination polymer with bridging bis(thiosemicarbazone) ligands and unsupported argentophilic interactions
Published in Journal of Coordination Chemistry, 2022
Sophie A. Crouch, Patrick R.W.J. Davey, Craig M. Forsyth, Stuart R. Batten, Brett M. Paterson
Silver salts and other reagents and solvents were obtained from standard commercial sources and were used as received. Nuclear magnetic resonance spectroscopy was recorded on a Bruker AVANCE III (1H NMR at 400.13 MHz and 19F{1H} at 376.15 MHz). Spectra were processed using BRUKER TopSpin 4.04 software. Deuterated solvents were obtained from Merck and Cambridge Isotope Laboratories Inc. Chemical shifts (δ) are reported in parts per million (ppm) with respect to residual solvent peaks (DMSO-d6 for 1H and trifluoroacetic acid for 19F{1H} NMR spectra). NMR spectra were recorded at 25 °C. Glyoxal-bis(4-phenyl-3-thiosemicarbazone) (H2gtsp) was synthesized according to the published procedure [12, 13].
New Ru PNP complexes as in situ Ru-oxo precursors in styrene and octane oxidation
Published in Journal of Coordination Chemistry, 2022
Dunesha Naicker, Saba Alapour, Sizwe J. Zamisa, Holger B. Friedrich
All experiments were performed using standard Schlenk techniques under inert conditions in moisture free glassware with anhydrous solvents. All solvents were analytical grade. To render the reaction glassware moisture free, it was heated with a heat gun followed by cycles of vacuum and nitrogen pressure. Deuterated solvents were used as received and stored in a vacuum desiccator. The NMR spectra were recorded at 400 MHz (1H), 100 MHz (13C) and 162 MHz (31P) using a Bruker ultrashield 400 MHz spectrometer. 1H NMR and 13C NMR chemical shifts are reported in parts per million (ppm) downfield from tetramethylsilane. 1H NMR and 13C NMR signals were referenced to the residual signal of CDCl3 (7.26 ppm) and (77.0 ppm), respectively. 31P NMR chemical shifts were reported in parts per million (ppm) from triphenylphosphine. Elemental analyses were carried out on a ThermoScientific Flash2000 Organic Elemental Analyser. All PNP ligands were synthesized with modification of literature procedure [42]. The precursor, RuCl2(PPh3)3, was purchased from Sigma Aldrich. (NMR spectra are shown in Supporting Information).