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Temperature dependence of the isotropic hyperfine coupling constants in 1,4‐hydroquinone and 1,4‐dihydroxynaphthalene cation radicals
Author(s) -
Eloranta Jussi,
Vuolle Mikko
Publication year - 1998
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199802)36:2<98::aid-omr228>3.0.co;2-q
Subject(s) - chemistry , radical , nitromethane , hydroquinone , proton , hyperfine coupling , electron paramagnetic resonance , hyperfine structure , coupling constant , isotropy , ring (chemistry) , atmospheric temperature range , analytical chemistry (journal) , computational chemistry , nuclear magnetic resonance , atomic physics , thermodynamics , organic chemistry , physics , quantum mechanics , particle physics
The temperature dependences of hydroxyl group proton and ring proton isotropic hyperfine coupling constants (IHFC) of 1,4‐hydroquinone (HQ) and 1,4‐dihydroxynaphthalene (NQ) cation radicals were measured by electron paramagnetic resonance spectroscopy. The spectral parameters were obtained in the temperature range 150–300 K using various solvents. The hydroxyl group proton IHFC data obtained were fitted to the theoretical temperature dependence model, yielding the hydroxyl group rotation barrier height and completely planar hydroxyl proton IHFC value. Experimental results are discussed with reference to theoretical density functional calculations. The new experimental rotation barrier heights for HQ and NQ cation radicals are 59±4 and 37±4 kJ mol ‐1 in nitromethane, respectively. © 1998 John Wiley & Sons, Ltd.