Zero-field nuclear magnetic resonance spectroscopy of viscous liquids

Abstract

a b s t r a c tWe report zero-field NMR measurements of a viscous organic liquid, ethylene glycol. Zero-field spectra were taken showing resolved scalar spin-spin coupling (J-coupling) for ethylene glycol at different temperatures and water contents. Molecular dynamics strongly affects the resonance linewidth, which closely follows viscosity. Quantum chemical calculations have been used to obtain the relative stability and coupling constants of all ethylene glycol conformers. The results show the potential of zero-field NMR as a probe of molecular structure and dynamics in a wide range of environments, including viscous fluids.

Association of symmetrical alkane diols with pyridine: DFT/GIAO calculation of 1H NMR chemical shifts

“…On the basis of coupling constants, it is estimated that for ethane‐1,2‐diol, 1 , trans conformers represent 0–5% in chloroform, 13–16% in acetonitrile, and about 32% in dimethylsulfoxide (DMSO) . In recent work, high‐level calculations on all ten conformers of ethane‐1,2‐diol, 1 , in a chloroform continuum find a (G + G′)/T ratio of 95 : 5 and overall Boltzmann‐weighted coupling constants of 3.4 and 6.7 Hz, in better agreement with our experimental values (3.7 and 6.5 Hz) than those cited (2.6 and 6.4 Hz) . The energy and coupling constant calculations are, therefore, virtually self‐consistent.…”

Zero-field NMR J-Spectroscopy of Organophosphorus Compounds

“…In recent years, zero-field nuclear magnetic resonance (NMR) has been demonstrated as an alternative NMR modality enabling identification, characterization, and quantification of molecular structures, through observation of unique J-coupling information. [1][2][3][4][5][6] The basic principle of zero-field NMR spectroscopy is access to indirect spin-spin interactions (Jcoupling) due to a vanishing Zeeman interaction in the absence of an applied magnetic field, 7,8 and averaged out direct spin-spin couplings occurring in isotropic liquids. 9 Owing to J-coupling, yielding useful information about the electronic structure and conformation of molecules, zero-field NMR can be used for chemical analysis and fingerprinting.…”

Zero-Field NMR J-Spectroscopy of Organophosphorus Compounds

“…In recent years, zero-field nuclear magnetic resonance (NMR) has been demonstrated as an alternative NMR modality enabling identification, characterization, and quantification of molecular structures, through observation of unique J -coupling information. − The basic principle of zero-field NMR spectroscopy is access to indirect spin–spin interactions ( J -coupling) due to a vanishing Zeeman interaction in the absence of an applied magnetic field, , and averaged out direct spin–spin couplings occurring in isotropic liquids . Owing to J -coupling, yielding useful information about the electronic structure and conformation of molecules, zero-field NMR can be used for chemical analysis and fingerprinting. , Zero-field NMR enables the high-resolution measurement of spin–spin couplings with remarkably narrow resonance line widths as a result of the high absolute field homogeneity and long spin coherence times. , Furthermore, the greater skin depth at low frequencies enables measurement of samples and monitorization of chemical reactions inside metal containers .…”