Nuclear Spin Relaxation in Methanol. The Effect of Proton Exchange

1967 ◽  
Vol 47 (3) ◽  
pp. 1112-1116 ◽  
Author(s):  
Michael Cocivera
Keyword(s):  
Spin Relaxation ◽  
Nuclear Spin ◽  
Proton Exchange ◽  
Nuclear Spin Relaxation

scholarly journals Functional Group Resolved Nuclear Spin Relaxation in Porous Media

2021 ◽  
Author(s):  
Neil Robinson ◽  
Eric May ◽  
Michael Johns
Keyword(s):  
Spin Relaxation ◽  
Nuclear Spin ◽  
Functional Group ◽  
Proton Exchange ◽  
Nuclear Spin Relaxation ◽  
Separation Processes ◽  
Diverse Range ◽  
Non Invasive ◽  
Relaxation Measurements ◽  
Low Magnetic Field

Understanding solid-fluid interactions within porous materials is critical for their efficient utilisation across chemical reaction and separation processes. However, detailed characterisation of interfacial phenomena within such systems is hampered by their optically opaque nature. Motivated by the need to bridge this capability gap, we detail here the application of low magnetic field 2D <sup>1</sup>H nuclear spin relaxation measurements as a non-invasive probe of sorbate/sorbent interactions, exploring the relaxation characteristics exhibited by liquid adsorbates confined to a model mesoporous silica. For the first time, we demonstrate the capacity of such measurements to distinguish functional group-specific relaxation phenomena across a diverse range of protic adsorbates of wide importance as solvents, reagents, and hydrogen carriers, with distinct relaxation environments assigned to the alkyl and hydroxyl moieties of the confined liquids. Uniquely, this relaxation behaviour is shown to correlate with adsorbate acidity, with the observed relationship rationalised on the basis of surface-adsorbate proton exchange dynamics.

scholarly journals Functional Group Resolved Nuclear Spin Relaxation in Porous Media

2021 ◽  
Author(s):  
Neil Robinson ◽  
Eric May ◽  
Michael Johns
Keyword(s):  
Spin Relaxation ◽  
Nuclear Spin ◽  
Functional Group ◽  
Proton Exchange ◽  
Nuclear Spin Relaxation ◽  
Separation Processes ◽  
Diverse Range ◽  
Non Invasive ◽  
Relaxation Measurements ◽  
Low Magnetic Field

Understanding solid-fluid interactions within porous materials is critical for their efficient utilisation across chemical reaction and separation processes. However, detailed characterisation of interfacial phenomena within such systems is hampered by their optically opaque nature. Motivated by the need to bridge this capability gap, we detail here the application of low magnetic field 2D <sup>1</sup>H nuclear spin relaxation measurements as a non-invasive probe of sorbate/sorbent interactions, exploring the relaxation characteristics exhibited by liquid adsorbates confined to a model mesoporous silica. For the first time, we demonstrate the capacity of such measurements to distinguish functional group-specific relaxation phenomena across a diverse range of protic adsorbates of wide importance as solvents, reagents, and hydrogen carriers, with distinct relaxation environments assigned to the alkyl and hydroxyl moieties of the confined liquids. Uniquely, this relaxation behaviour is shown to correlate with adsorbate acidity, with the observed relationship rationalised on the basis of surface-adsorbate proton exchange dynamics.

The dynamics of water in heterogeneous systems

1977 ◽  
Vol 278 (959) ◽  
pp. 59-87 ◽  
Keyword(s):  
Neutron Scattering ◽  
Spin Relaxation ◽  
Nuclear Spin ◽  
Heterogeneous Systems ◽  
Proton Exchange ◽  
Nuclear Spin Relaxation ◽  
Water Molecules ◽  
Pure Liquid ◽  
Quasielastic Neutron ◽  
Nuclear Magnetic

The basic principles of nuclear spin relaxation, dielectric relaxation and quasielastic neutron scattering and their use in studying the motions of water molecules are outlined. A summary is given of the time scales associated with the translational and rotational motions of water molecules and of intermolecular proton exchange in pure liquid water. A model is then proposed for the dynamics of water molecules in heterogeneous systems involving regions having differing compositions, water molecules within each region existing in environments both affected by interaction with the macromolecular components and free of their influence and including exchange of water molecules between different environments and regions. The lifetime of the interaction of water molecules with the macromolecular components is assumed long compared with the time for rotation of such bound molecules. Exchange of protons between water molecules and between water molecules and macromolecules is also considered. The ways in which such processes would be expected to affect the observed nuclear magnetic resonance, dielectric and neutron scattering behaviour are outlined. Particular emphasis is placed on nuclear spin relaxation phenomena and the existence and observation of residual dipolar and quadrupolar splittings in the n.m.r. spectra of 1 H and 2 H (D) nuclei in water molecules in such systems, these splittings arising from water molecules dynamically oriented at water/macromolecule interfaces. Details are then given of particular studies of water molecule dynamics in heterogeneous systems using n.m.r., dielectric and neutron scattering techniques. The systems discussed include moist protein powders, protein solutions, phospholipid/ water and soap/water mesophases, clay/water systems and biological polymers and tissues. It is concluded that water in these systems is highly mobile, that water molecules affected directly by a macromolecule tumble anisotropically about all axes relative to the macromolecule with correlation times in the region of 10 -9 s at 260 K and that these molecules exchange with water molecules free of the influence of the macromolecule with a lifetime in the dynamically oriented state of the order of 10 -6 s at temperatures around 300 K. The ability of nuclear magnetic relaxation studies to distinguish water in different regions of a tissue is discussed and examples are given of the study of the rate of water transport across membranes using these techniques.

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