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Communication: Synperiplanar to antiperiplanar conformation changes as underlying the mechanism of Debye process in supercooled ibuprofen.
- Source :
- Journal of Chemical Physics; Sep2013, Vol. 139 Issue 11, p111103, 4p, 1 Diagram, 3 Graphs
- Publication Year :
- 2013
-
Abstract
- In this Communication, we present experimental studies that put new insight into the puzzling nature of the Debye relaxation found in the supercooled liquid state of racemic ibuprofen. The appearance of D-relaxation in the loss spectra of non-hydrogen bonding methylated derivate of ibuprofen has proven that Debye relaxation is related solely with conformational changes of the carboxyl group, termed in this paper as synperiplanar-antiperiplanar. Our studies indicate that the presence of hydrogen bonding capabilities is not here the necessary condition to observe Debye process, however, their occurrence might strongly influence α- and D-relaxations dynamics. Interestingly, the activation energy of the D-process in ibuprofen methyl ester on approaching T<subscript>g</subscript> was found to be perfectly consistent with that reported for ibuprofen by Affouard and Correia [J. Phys. Chem. B 114, 11397-11402 (2010)] (∼39 kJ/mol). Finally, IR measurements suggest that the equilibrium between conformers concentration depends on time and temperature, which might explain why the appearance of D-relaxation in supercooled ibuprofen depends on thermal history of the sample. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00219606
- Volume :
- 139
- Issue :
- 11
- Database :
- Complementary Index
- Journal :
- Journal of Chemical Physics
- Publication Type :
- Academic Journal
- Accession number :
- 90360493
- Full Text :
- https://doi.org/10.1063/1.4820492