S. Simova et Hj. Schneider, NMR analyses of cyclodextrin complexes with substituted benzoic acids and benzoate anions, J CHEM S P2, (8), 2000, pp. 1717-1722
Citations number
32
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
Inclusion modes of alpha-cyclodextrin with para-substituted benzoic acids (
X=H, OH, CH3, CN, NO2) and the corresponding anions are analyzed with NOEs
from ROESY experiments and with H-1 NMR shielding variations. The data indi
cate a predominant deep inclusion of the carboxy group in the complexes wit
h all substituted benzoic acids, irrespective of the nature of the substitu
ents. Protons in ortho- and meta-positions to the carboxylic group show com
plexation shifts larger than medium-induced shifts observed for any solvent
. Complexation-induced C-13 NMR shift (CIS) changes of the phenyl derivativ
es are also measured, with partial correction of literature signal assignme
nts. Measurements of the same derivatives in several aprotic solvents revea
l no correlation with complexation induced shifts, showing that polarity ef
fects resulting from the medium cannot be the major source of the observed
CIS values.