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13 C, 14 N, 15 N and 17 O NMR spectra of the charged species of nitropyrroles and nitroimidazoles
Author(s) -
Lippmaa E.,
Mägi M.,
Novikov S. S.,
Khmelnitski L. I.,
Prihodko A. S.,
Lebedev O. V.,
Epishina L. V.
Publication year - 1972
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.1270040202
Subject(s) - chemistry , protonation , ring (chemistry) , nitro , chemical shift , excited state , ion , conjugated system , diamagnetism , spectral line , paramagnetism , nmr spectra database , photochemistry , organic chemistry , atomic physics , alkyl , physics , quantum mechanics , astronomy , magnetic field , polymer
Changes in 13 C and 14 N chemical shifts of the nitro derivatives of nitrogen heterocycles upon ionization (anion or cation formation) are twofold—first a uniform paramagnetic or in the case of protonation, a uniform diamagnetic shift of all the ring resonances that parallels the changes in the respective ultraviolet spectra and must be caused by changes in the molecular excited states, and second—the influence of the conjugated nitro group. About one third of the total negative anion charge may be localized on the nitro group, which causes unusually large shifts of the ring 13 C resonances in this case.