Conformational equilibria in N,3- and N,4-dimethylpiperidine

Abstract

The conformational equilibrium free energy difference for the C-methyl group in N,3- and N,4-dimethylpiperidine, and therefore in 3- and 4-methylpiperidine to a good approximation, have been estimated to be 6.3 ± 0.3 and 8.3 ± 0.3 kJ mol^–1 at 293 K in dodecane as solvent, using the ratios of diastereomeric ions formed by the kinetically controlled protonation of ¹³C isotopically enriched derivatives.