(1)H-(17)O nuclear-quadrupole double-resonance study of hydrogen disorder in 2-nitrobenzoic acid.
J Magn Reson
; 144(1): 13-9, 2000 May.
Article
em En
| MEDLINE
| ID: mdl-10783269
ABSTRACT
Temperature dependence of (17)O nuclear quadrupole resonance frequencies was measured in solid 2-nitrobenzoic acid by a (1)H-(17)O nuclear quadrupole double resonance technique. The experimental results show the presence of a fast exchange of hydrogen atoms between two nonequivalent positions within the O-H ellipsis O hydrogen bonds. The hydrogen disorder is ascribed to concerted jumps of two hydrogen atoms within the hydrogen bonds connecting two molecules in a dimer. The energy difference DeltaE of the two hydrogen configurations is equal to DeltaE = 60 meV = 5.8 kJ/mol. The dipole structure of the (17)O NQR lines from the C-O-H oxygen positions was also measured at -100 degrees C and at room temperature. The orientation of the principal axes of the electric field gradient tensor with respect to the O-H bond and the sign of the quadrupole coupling constant were determined. The oxygen-hydrogen distance R(O-H), as determined from the dipole structure of the (17)O NQR lines is at -100 degrees C equal to 0.099 nm. At room temperature we observe a longer distance, R(O-H) = 0.101 nm, in agreement with the hydrogen intrabond exchange.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Benzoatos
/
Espectroscopia de Ressonância Magnética
Idioma:
En
Revista:
J Magn Reson
Assunto da revista:
DIAGNOSTICO POR IMAGEM
Ano de publicação:
2000
Tipo de documento:
Article
País de afiliação:
Eslovênia