An unusually short inter-molecular N-H⋯N hydrogen bond in crystals of the hemi-hydro-chloride salt of 1- exo -acetamido-pyrrolizidine

• Published in: Acta crystallographica. Section E, Crystallographic communications Vol. 76; no. Pt 1; pp. 77 - 81
• Main Authors: Bhardwaj, Minakshi, Ai, Qianxiang, Parkin, Sean R, Grossman, Robert B
• Format: Journal Article
• Language: English
• Published: England International Union of Crystallography 01-01-2020
• Subjects: Research Communications; crystal structure; short N—H⋯N hydrogen bond
• ISSN: 2056-9890; 2056-9890
• DOI: 10.1107/S2056989019016517

The title compound [systematic name: (1
*, 8
)-2-acetamidoocta-hydro-pyrrol-izin-4-ium chloride-
-[(1
, 8
)-hexa-hydro-1
-pyrrolizin-2-yl)acetamide (1/1)], 2(C
H
N
O)·HCl or C
H
N
O
·Cl
·C
H
N
O, arose as an unexpected product when 1-
-acetamido-pyrrolizidine (AcAP; C
H
N
O) was dissolved in CHCl
. Within the AcAP pyrrolizidine group, the unsubstituted five-membered ring is disordered over two orientations in a 0.897 (5):0.103 (5) ratio. Two AcAP mol-ecules related by a crystallographic twofold axis link to H
and Cl
ions lying on the rotation axis, thereby forming N-H⋯N and N-H⋯Cl⋯H-N hydrogen bonds. The first of these has an unusually short N⋯N separation of 2.616 (2) Å: refinement of different models against the present data set could not distinguish between a symmetrical hydrogen bond (H atom lying on the twofold axis and equidistant from the N atoms) or static or dynamic disorder models (
N-H⋯N + N⋯H-N). Computational studies suggest that the disorder model is slightly more stable, but the energy difference is very small.