Premium
Saturated amine oxides: Part 8 †. Hydroacridines: Part 27 ‡. Effects of N ‐oxidation and of N ‐quaternization on the 15 N NMR chemical shifts of N ‐methylpiperidine‐derived mono‐, bi‐, and tricycloaliphatic tertiary amines
Author(s) -
Potmischil Francisc,
Duddeck Helmut,
Nicolescu Alina,
Deleanu Calin
Publication year - 2007
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.1951
Subject(s) - chemistry , chemical shift , piperidine , alkyl , inductive effect , medicinal chemistry , ring (chemistry) , oxygen , amine gas treating , oxygen atom , tertiary amine , stereochemistry , ring size , molecule , organic chemistry
Abstract The 15 N chemical shifts of 13 N ‐methylpiperidine‐derived mono‐, bi‐ and tricycloaliphatic tertiary amines, their methiodides and their N ‐epimeric pairs of N ‐oxides were measured, and the contributions of specific structural parameters to the chemical shifts were determined by multilinear regression analysis. Within the examined compounds, the effects of N ‐oxidation upon the 15 N chemical shifts of the amines vary from +56 ppm to +90 ppm (deshielding), of which approx. +67.7 ppm is due to the inductive effect of the incoming N + O − oxygen atom, whereas the rest is due to the additive shift effects of the various C ‐alkyl substituents of the piperidine ring. The effects of quaternization vary from −3.1 ppm to +29.3 ppm, of which approx. +8.9 ppm is due to the inductive effect of the incoming N + CH 3 methyl group, and the rest is due to the additive shift effects of the various C ‐alkyl substituents of the piperidine ring. The shift effects of the C ‐alkyl substituents in the amines, the N ‐oxides and the methiodides are discussed. Copyright © 2007 John Wiley & Sons, Ltd.