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.
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.
Potmischil
Francisc
F
Department of Organic Chemistry, University of Bucharest, Bulevardul Regina Elisabeta 4-12, RO-030018 Bucharest-1, Romania. potmisch@yahoo.com
Duddeck
Helmut
H
Nicolescu
Alina
A
Deleanu
Calin
C
D000166:Acridines / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards*; D008969:Molecular Sequence Data; D009587:Nitrogen Isotopes; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry*; D012015:Reference Standards; D012680:Sensitivity and Specificity; D013237:Stereoisomerism
D000166:Acridines; D000588:Amines; D009587:Nitrogen Isotopes; D010087:Oxides; D010880:Piperidines; C059226:N-methylpiperidine