Autor(es):
Jarmelo, Susana 
; Fausto, Rui
Data: 2002
Identificador Persistente: http://hdl.handle.net/10316/10720
Origem: Estudo Geral - Universidade de Coimbra
Detalhes do Documento
Structure and vibrational spectra of -hydroxy isobutyric acid in the crystallin...
Descrição
Infrared spectra of monomeric -hydroxy isobutyric acid (HIBA) isolated in argon, krypton and xenon matrixes (at 8 K) are reported. It is shown that in all the studied matrixes HIBA exists preferentially as the intramolecularly H-bonded SsC conformer, where the HOCC, OCCO and OCOH dihedrals are 0°. In addition to the SsC form, two higher energy conformers (AaT and GskC) could be observed experimentally for the first time. The spectra of the three observed conformers were assigned on the basis of density functional theory calculations (B3LYP/6-31G*) and their relative energies estimated from relative band intensities. Raman and infrared spectra of both crystalline and low temperature glassy states were also recorded and interpreted. In consonance with previously reported X-ray structural studies (W. P. J. Gaykema, J. A. Kanters and G. Roelofsen, Cryst. Struct. Commun., 1978, 7, 463), the vibrational data now obtained are consistent with the exclusive presence in the crystalline phase of molecules assuming a conformation similar to that of the lowest energy monomer observed in the matrixes (SsC conformer). http://dx.doi.org/10.1039/b110949a Fundação para a Ciência e Tecnologia (PRAXIS QUI/10137/98), M.Sc. Grant ref. SFRH/157/2000 (Susana Jarmelo).
Infrared spectra of monomeric -hydroxy isobutyric acid (HIBA) isolated in argon, krypton and xenon matrixes (at 8 K) are reported. It is shown that in all the studied matrixes HIBA exists preferentially as the intramolecularly H-bonded SsC conformer, where the HOCC, OCCO and OCOH dihedrals are 0°. In addition to the SsC form, two higher energy conformers (AaT and GskC) could be observed experimentally for the first time. The spectra of the three observed conformers were assigned on the basis of density functional theory calculations (B3LYP/6-31G*) and their relative energies estimated from relative band intensities. Raman and infrared spectra of both crystalline and low temperature glassy states were also recorded and interpreted. In consonance with previously reported X-ray structural studies (W. P. J. Gaykema, J. A. Kanters and G. Roelofsen, Cryst. Struct. Commun., 1978, 7, 463), the vibrational data now obtained are consistent with the exclusive presence in the crystalline phase of molecules assuming a conformation similar to that of the lowest energy monomer observed in the matrixes (SsC conformer). http://dx.doi.org/10.1039/b110949a Fundação para a Ciência e Tecnologia (PRAXIS QUI/10137/98), M.Sc. Grant ref. SFRH/157/2000 (Susana Jarmelo).
Tipo de Documento
Artigo
Idioma Inglês
Idioma Inglês
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