Substituent effects on 15N NMR chemical shifts in selected N-alkylthiohydroxamic acids. A comparative study.
The 15N NMR spectra of three N-alkyl-delta-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 15N 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 sigma+ parameter.
Przychodzeń
Witold
W
Faculty of Chemistry, Gdańsk University of Technology, 80-952 Gdańsk, Poland. witold@chem.pg.gda.pl
Doszczak
Leszek
L
Rachon
Janusz
J
D000478:Alkylation; D006877:Hydroxamic Acids / Q000737:chemistry*; D006898:Hydroxylamines / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008968:Molecular Conformation; D009587:Nitrogen Isotopes; D013438:Sulfhydryl Compounds / Q000737:chemistry
D006877:Hydroxamic Acids; D006898:Hydroxylamines; D009587:Nitrogen Isotopes; D013438:Sulfhydryl Compounds; C018338:N-methylhydroxylamine