Premium
Nuclear magnetic resonance study of the configurational equilibria of ranitidine in solution
Author(s) -
Geraldes Carlos F. G. C.,
Gil Victor M. S.,
Teixeira M. Helena S. F.,
Teixeira F.
Publication year - 1987
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260250305
Subject(s) - chemistry , moiety , isomerization , intramolecular force , aqueous solution , proton nmr , protonation , nuclear magnetic resonance spectroscopy , hydrogen bond , medicinal chemistry , stereochemistry , crystallography , organic chemistry , molecule , catalysis , ion
The E/Z configurational equilibrium of the nitroethylenic moiety of the antiulcer agent ranitidine was studied in aqueous solution and in DMSO‐ d 6 and CDCl 3 using 1 H and 13 C NMR spectroscopy. In aqueous solution the room temperature E/Z isomerization of the unprotonated nitroketenediamine moiety is fast on the NMR time scale, but becomes slow for the species protonated at this moiety owing to intramolecular hydrogen bonding between the nitro group and a neighbouring NH 2 R + group. In DMSO‐ d 6 a free energy of activation of the order of 70 kJ mol −1 was estimated for the E/Z isomerization of the unprotonated moiety of ranitidine, in good agreement with values previously found for 2,2‐disubstituted nitroethylene model compounds.