Differences between DeltaH and DeltaS Values of the 1:2 Complexes of Camphor Enantiomers with alfa-Cyclodextrin Determined by NMR Titrations and by Other Techniques

• Autorzy: Dodziuk H. , Kozminski W. , Dolgonos G.
• Języki publikacji: EN

Abstrakty

EN

DeltaH12 andDeltaS12 values for the 1:2 complexes of camphor enantiomers with alfa-cyclodextrin by NMR titrations, carried out from 25 to 48 graduateC, yielded -16.0 +-0.2 kcal/mol and 28.3 0.3 e.u. for 1a@2 and -9.8 0.2 kcal/mol and 9.10.2 e.u. for 1b@2. A comparison of the values obtained by other groups, using isothermal titration calorimetry and reversed-phase liquid hromatography, showed considerable differences except the Delta H12 and DeltaS12 for 1a@2, obtained by NMR and ITC methods. The reason of the differences, involving RPLC, are not discussed in view of internal inconsistencies of this method. On the other hand, the disagreement between the ITC andNMRresults seems to be due to the difference in solvents (H2O and D2O, respectively) used in both methods, which causes deuteration of all 36 OH groups of the host cyclodextrins. Interestingly, the deuteration causes a lowering of the absolute values of DeltaH12 and DeltaS12 for 1b@2, while the corresponding values of the complex with the second enantiomer are either unchanged or undergo only small changes upon the complexation.

Słowa kluczowe

EN

chiral recognition; cyclodextrin; NMR; thermodynamic parameters; isotope effect

• Wydawca: Polskie Towarzystwo Chemiczne
• Czasopismo: Polish Journal of Chemistry
• Rocznik: 2003
• Tom: Vol. 77 / nr 2
• Strony: 251--255
• Opis fizyczny: Bibliogr. 14 poz., rys.

Twórcy

autor

Dodziuk H.

• Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland

autor

Kozminski W.

• Department of Chemistry, Warsaw University, Pasteura 1, 02-093 Warsaw, Poland

autor

Dolgonos G.

• Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland

Bibliografia

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• 8. Dodziuk H., Ejchart A., Lukin O. and Vysotsky M.O., J. Org. Chem., 64, 1503 (1999).
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• 11. Dodziuk H., Nowinski K.S., Kozminski W. and Dolgonos G., Org. Biomol. Chem., submitted for publication.
• 12. Dodziuk H., Schmidtchen F., Kozminski W. and Dolgonos G., poster P-124, “Chiral recognition of camphor enantiomers by a-cyclodextrin: a comparison of enthalpy and entropy for the complex formation obtained by microcalorimetry, NMR and chromatography”, 13th International Symposium Chirality 2001, Orlando, USA, July 2001.
• 13. Ref. 1, Chapter 7.4.
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