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Substituent effects on 15 N NMR chemical shifts in selected N ‐alkylthiohydroxamic acids. A comparative study
Author(s) -
Przychodzeń Witold,
Doszczak Leszek,
Rachon Janusz
Publication year - 2005
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/mrc.1497
Subject(s) - chemistry , chemical shift , steric effects , substituent , stereochemistry , ring (chemistry) , alkyl , additive function , nmr spectra database , medicinal chemistry , proton nmr , computational chemistry , spectral line , organic chemistry , mathematical analysis , physics , mathematics , astronomy
The 15 N NMR spectra of three N ‐alkyl‐δ‐carbomethoxyvalerothiohydroxamic acids ( 2 ) and six synthesized N ‐isopropylbenzothiohydroxamic acids ( 3 ) were measured and compared with appropriate spectra of structurally similar hydroxylamines ( 1 ), benzohydroxamic acids ( 4 ), benzamides ( 5 ) and thiobenzamides ( 6 ). The analysis of the chemical shifts of the thiohydroxamic acids under investigation indicates that the inductive effect of the hydroxyl group rather than steric hindrance is responsible for non‐additivity of the effect of substituents. Additionally, N ‐hydroxyl diminishes the effect of aromatic ring substituents on the 15 N chemical shifts in the thiohydroxamic acids 3 which is approximately half that in the respective thiobenzamides 6 . The chemical shift values correlate best with Brown's σ + parameter. Copyright © 2004 John Wiley & Sons, Ltd.