Saturated 5-membered ring conformations. 2—1H NMR study of protonated N-methylpyrrolidines

The ¹H NMR spectra of the protonated and unprotonated forms of cis- and trans-N-methylhexahydroisoindoline, of 1,3,3,4,4-pentamethylpyrrolidine and of 1,3,3-trimethylpyrrolidine were analyzed. The coupling constants between the NH⊕ and the CH protons α to the nitrogen allowed the study of the conformation of the cyclic systems in pseudorotation.