^<13>C NMR Spectral Behavior of N-Substituted-4-piperidones in Methanol. Possibility of Distinguishing between Acetal and Hemiacetal

Abstract

The behavior of several N-substituted-4-piperidones in methanol has been studied by ¹³C nuclear magnetic resonance (NMR) spectroscopy. All the piperidones studied were found to be equilibrium with their hemiacetals in methanolic solutions. The features of N-acyl derivatives were different from those of N-alkyl derivatives and the differences could be accounted for by electronic factors. The chemical shifts of the acetals were also determined and a procedure for distinguishing between hemiacetal and acetal is proposed.