How does β-cyclodextrin affect the aggregation of sodium perfluoroheptanoate in aqueous solution: a 19F NMR study

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• 作者：Sérgio Lima ; Cristiano Andrade-Dias ; Ana M. A. Dias ; Isabel M. Marrucho ; Jo?o A. P. Coutinho and José J. C. Teixeira-Dias
• 关键词：Aqueous solution ; β ; Cyclodextrin ; Critical micellar concentration ; Inclusion ; NMR chemical shifts ; Self ; association ; Sodium perfluoroheptanoate
• 刊名：Journal of Inclusion Phenomena and Macrocyclic Chemistry
• 出版年：2007
• 出版时间：April, 2007
• 年：2007
• 卷：57
• 期：1-4
• 页码：157-162
• 全文大小：219.7 KB
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Chemistry
  Organic Chemistry
  Food Science
  Crystallography
  
• 出版者：Springer Netherlands
• ISSN：1573-1111

文摘

1H and 19F NMR spectra were recorded for D₂O solutions of sodium perfluoroheptanoate with defined concentrations up to 200 mM, in the absence and presence of β-cyclodextrin (15 mM). Analysis of 1H chemical shift data obtained by the method of continuous variations (Job’s method) confirms the formation of 1:1 inclusion complexes for the perfluoroheptanote anion in β-cyclodextrin and leads to an estimate for the apparent inclusion constant (≥104 M?1). In addition, analysis of 19F chemical shift data based on two simplifying assumptions (monodisperse perfluoroheptanoate solutions below the critical micellar concentration (CMC), and a single self-associated state after the CMC) enables to interpret all the experimental chemical shift data and allows to determine CMC values for the absence and presence of β-cyclodextrin (104 and 116 mM). It is shown that the self-association of perfluoroheptanoate and its inclusion in β-cyclodextrin lead to shielding and deshielding of the fluorine atoms, respectively.