Saturated amine oxides: Part 8†. Hydroacridines: Part 27‡. Effects of N‐oxidation and of N‐quaternization on the 15N NMR chemical shifts of N‐methylpiperidine‐derived mono‐, bi‐, and tricycloaliphatic tertiary amines
- 15 January 2007
- journal article
- Published by Wiley in Magnetic Resonance in Chemistry
- Vol. 45 (3) , 231-235
Abstract
The 15N 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 15N 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+CH3 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.Keywords
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