13C Chemical shifts and conformational equilibria in quaternary piperidinium salts

Carbon-13 nuclear magnetic resonance spectra of a series of N-methyl-N-alkylpiperidinium salts have been measured, and the observed chemical shifts analysed in terms of the stereochemical and conformational properties of the molecules. Furthermore, the differences of the free energy (ΔG°) between two conformers on ring inversion have been estimated.