Exploiting Nuclear Spin Polarization to Investigate Free Radical Reactions via in situ NMR

2007 ◽  
pp. 125-154 ◽  
Author(s):  
Lars T. Kuhn ◽  
Joachim Bargon
Keyword(s):  
Free Radical ◽  
Spin Polarization ◽  
Nuclear Spin ◽  
Radical Reactions ◽  
Nuclear Spin Polarization ◽  
Free Radical Reactions ◽  
In Situ Nmr

Photochemistry of Pivalaldehyde in Solution Studied by CIDNP

1973 ◽  
Vol 51 (18) ◽  
pp. 3032-3038 ◽  
Author(s):  
Holger E. C. Chen ◽  
Arend Groen ◽  
Michael Cocivera
Keyword(s):  
Free Radicals ◽  
Spin Polarization ◽  
Nuclear Spin ◽  
The Other ◽  
Radical Reactions ◽  
Carbonyl Carbon ◽  
Nuclear Spin Polarization ◽  
Butyl Group ◽  
Spin Polarized ◽  
Tertiary Carbon

The n.m.r. spectrum observed during irradiation of pivalaldehyde dissolved in perfluoromethylcyclohexane indicates the formation of several compounds whose hydrogens are spin polarized. These compounds are 2-methylpropane, 2-methylpropene, and pivalaldehyde. A mechanism involving radical reactions which is consistent with these results is presented. According to this mechanism, the primary photochemical step is cleavage of the bond between the carbonyl carbon and the tertiary carbon of the t-butyl group. In contrast, this step does not appear to be important for acetaldehyde. As a test of the proposed mechanism CCl4 is added to trap free radicals. In this case, one of the products is CCl3COH. A mechanism for the formation of this and the other products having nuclear spin polarization is presented.

Dynamical Nuclear Polarization

2018 ◽  
Author(s):  
M. M. Glazov
Keyword(s):  
Spin Polarization ◽  
Nuclear Spin ◽  
Nuclear Polarization ◽  
Magnetic Moments ◽  
Nonlinear Effects ◽  
Many Body ◽  
Nuclear Spin Polarization ◽  
Optical Resonances ◽  
Dynamical Nuclear Polarization ◽  
Temperature Concept

The transfer of nonequilibrium spin polarization between the electron and nuclear subsystems is studied in detail. Usually, a thermal orientation of nuclei in magnetic field is negligible due to their small magnetic moments, but if electron spins are optically oriented, efficient nuclear spin polarization can occur. The microscopic approach to the dynamical nuclear polarization effect based on the kinetic equation method, along with a phenomenological but very powerful description of dynamical nuclear polarization in terms of the nuclear spin temperature concept is given. In this way, one can account for the interaction between neighbouring nuclei without solving a complex many-body problem. The hyperfine interaction also induces the feedback of polarized nuclei on the electron spin system giving rise to a number of nonlinear effects: bistability of nuclear spin polarization and anomalous Hanle effect, dragging and locking of optical resonances in quantum dots. Theory is illustrated by experimental data on dynamical nuclear polarization.

The initial reaction mechanism and thermal sensitivity of a fluoropolymer-containing energetic molecular system: the coupling effect of interfacial interactions and free radical reactions

CrystEngComm ◽  
2021 ◽  
Vol 23 (16) ◽  
pp. 3006-3014
Author(s):  
Wen Qian
Keyword(s):  
Free Radical ◽  
Coupling Effect ◽  
Molecular System ◽  
Thermal Sensitivity ◽  
Radical Reactions ◽  
Initial Reaction ◽  
Interfacial Interactions ◽  
Free Radical Reactions ◽  
Molecular Systems ◽  
Reactive Molecular Dynamics

A strategy combining classic and reactive molecular dynamics is applied to find the coupling effect of interfacial interactions and free radical reactions during the initial thermal decomposition of fluoropolymer-containing molecular systems.

Further studies on free-radical pathology in the major central nervous system disorders: effect of very high doses of methylprednisolone on the functional outcome, morphology, and chemistry of experimental spinal cord impact injury

1982 ◽  
Vol 60 (11) ◽  
pp. 1415-1424 ◽  
Author(s):  
H. B. Demopoulos ◽  
E. S. Flamm ◽  
M. L. Seligman ◽  
D. D. Pietronigro ◽  
J. Tomasula ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Nervous System ◽  
Free Radical ◽  
Tissue Injury ◽  
Functional Restoration ◽  
Radical Reactions ◽  
Free Radical Reactions ◽  
Cord Injury

The hypothesis that pathologic free-radical reactions are initiated and catalyzed in the major central nervous system (CNS) disorders has been further supported by the current acute spinal cord injury work that has demonstrated the appearance of specific, cholesterol free-radical oxidation products. The significance of these products is suggested by the fact that: (i) they increase with time after injury; (ii) their production is curtailed with a steroidal antioxidant; (iii) high antioxidant doses of the steroidal antioxidant which curtail the development of free-radical product prevent tissue degeneration and permit functional restoration. The role of pathologic free-radical reactions is also inferred from the loss of ascorbic acid, a principal CNS antioxidant, and of extractable cholesterol. These losses are also prevented by the steroidal antioxidant. This model system is among others in the CNS which offer distinctive opportunities to study, in vivo, the onset and progression of membrane damaging free-radical reactions within well-defined parameters of time, extent of tissue injury, correlation with changes in membrane enzymes, and correlation with readily measurable in vivo functions.

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