Pyrrolidine, pseudorotation

In pyrrolidine and its chlorine and /V-methyl derivatives the barrier for pseudorotation is 1.66, 2.98, and 2.8 kcal/mol, respectively. The E structures are stable. Puckering dynamics in pyrrolidine was considered by Pfafferott et al. [1985]. 

The pyrrolidine molecule is practically without strain, nonplanar and conformationally mobile. As in the case with tetrahydrofuran (see p 67), the twist and envelope conformations are preferred. The activation energy for pseudorotation is 1.3 kJ mol". The chemical shifts in the NMR spectra lie in the region characteristic for cycloalkanes and dialkylamines. 

A similar treatment was necessary for pyrrolidine again the pseudorotation was found to be slightly restricted, if a satisfactory fit to the calorimetric data was to be obtained if pseudo-rotation was excluded no such fit was possible. 

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