The various internal rotations and interconfor- mational jumps of the Na-salt form of ibuprofen in the solid state were characterized in detail by means of the simultaneous analysis of a variety of low- and high-resolution NMR experi- ments aimed at measuring several 13C and 1H spectral and relaxation properties at different temperatures and frequencies. The results were first qualitatively analyzed to identify the motions of the different molecular fragments and to assign them to specific frequency regimes (slow, <103 Hz; intermediate, 103106 Hz; and fast, >106 Hz). Subsequently, a simultaneous fit of the experimental data sets most sensitive to each frequency range was performed by using suitable motional models, thus obtaining, for each motion, correlation times and activation energies. The motions so characterized were: the rotations of the three methyl groups and of the isobutyl group, occurring in the fast regime, and the π-flip of the phenyl ring, belonging to the intermediate motional regime. The results obtained for the Na-salt form were compared with those of the acidic form of ibuprofen, previously obtained from a similar solid-state NMR approach: despite the very similar chemical structure of the two compounds, their dynamic properties in the solid state are noticeably different.
|Autori interni:||CARIGNANI, ELISA|
|Autori:||Carignani E; Borsacchi S; Geppi M|
|Titolo:||Dynamics by Solid-State NMR: Detailed Study of Ibuprofen Na Salt and Comparison with Ibuprofen|
|Anno del prodotto:||2011|
|Digital Object Identifier (DOI):||10.1021/jp202650n|
|Appare nelle tipologie:||1.1 Articolo in rivista|