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An NMR, ESR, ENDOR and TRIPLE resonance investigation of a cation radical formed from 1,2,4,5‐tetramethoxybenzene
Author(s) -
Fairhurst S. A.,
Smith I. M.,
Sutcliffe L. H.,
Taylor S. M.
Publication year - 1982
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270180413
Subject(s) - chemistry , coupling constant , hyperfine coupling , radical , hyperfine structure , dichloromethane , electron paramagnetic resonance , resonance (particle physics) , reaction rate constant , solvent , spectral line , nuclear magnetic resonance , analytical chemistry (journal) , atomic physics , kinetics , organic chemistry , physics , particle physics , quantum mechanics , astronomy
Several methods have been established for preparing cation radicals from 1,2,4,5‐tetramethoxybenzene that allow highly resolved ESR spectra to be recorded. Precise values of the hyperfine coupling constants for the aromatic and methoxy protons have been obtained; the values are 0.2268±0.0004 and 0.0863±0.0002 mT, respectively, with dichloromethane as solvent. No temperature dependence is evident. TRIPLE resonance experiments showed that both coupling constants have the same sign. NMR experiments provided contact shift and line broadening measurements; these proved that both the above constants are positive and led to a value of 3.1 (±0.3)×10 8 M −1 s −1 at 23°C for the rate constant for electron exchange between the cation radical and the parent compound.