Determination of the absolute signs of 19F hyperfine coupling constants by chemically induced dynamic nuclear spin polarization (CIDNP) in fluorinated aromatic systems

1973 ◽  
Vol 59 (6) ◽  
pp. 3431-3432 ◽  
Author(s):  
M. R. Brinkman ◽  
D. Bethell ◽  
J. Hayes
Keyword(s):  
Spin Polarization ◽  
Nuclear Spin ◽  
Hyperfine Coupling ◽  
Coupling Constants ◽  
Nuclear Spin Polarization ◽  
Hyperfine Coupling Constants ◽  
Chemically Induced ◽  
Aromatic Systems ◽  
The Absolute

Chemically Induced Dynamic Nuclear Polarization During Irradiation of Phenol in the Presence of Amides

1975 ◽  
Vol 53 (16) ◽  
pp. 2459-2464
Author(s):  
Shiv P. Vaish ◽  
Holger E. Chen ◽  
Micha Tomkiewicz ◽  
Robert D. McAlpine ◽  
Michael Cocivera
Keyword(s):  
Carbonyl Group ◽  
Spin Polarization ◽  
Dynamic Nuclear Polarization ◽  
Nuclear Spin ◽  
Nuclear Polarization ◽  
Radical Pair ◽  
Hydroxybenzoic Acid ◽  
Nuclear Spin Polarization ◽  
Ph Values ◽  
Chemically Induced

Irradiation of D2O solutions containing various phenols with aliphatic amides at pH values between 9 and 12 results in nuclear spin polarization which is observed as n.m.r. emission signals during irradiation. No polarization is observed for the phenols which include tyrosine, cresol, p-hydroxybenzoic acid, phenol, and others. For the amides which include acetamide, propionamide, N-methylacetamide, and N,N-dimethylacetamide, polarization was observed for only the protons on the carbon bonded to the carbonyl group. Because excited phenolate ions are known to eject electrons, it is proposed that the radical RĊ(O−)NR2 is formed by reaction of the amide with the hydrated electron. The polarization observed for the amides can be explained by reaction of RĊ(O−)NR2 with a benzosemiquinone radical via a radical pair.

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