Determination of hydration equilibrium constants and pKa values of 4-piperidones in buffered water solutions

¹H and ¹³C chemical shift parameters are given for 4-piperidones and their derivatives in buffered aqueous solution. The ¹³C shift increments of methyl substituents on the nitrogen atom are discussed. The pH-shift dependence is studied in detail and pK_a values are given for ketone forms and hydration products. The hydration equilibria are measured as a function of pH and temperature.