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- Title
STUDY OF THE SELF-ASSOCIATION OF CAFFEINE AND CHLOROGENIC ACID AND THEIR HETERO-ASSOCIATION WITH METHYLENE BLUE USING SPECTROPHOTOMETRIC METHOD.
- Authors
DALGA, BEREKET; BELAY, ABEBE
- Abstract
The self-association of caffeine, chlorogenic acid and their hetero-association with Methylene Blue were studied in aqueous solution by UV/Visible spectrophotometry. The dimerization constants of caffeine and chlorogenic acid analyzed using dimer model at the wavelengths of 272.8 and 324 nm were found to be 565.33 and 1027 M-1 respectively. The heteroassociation constants of methylene blue with caffeine and chlorogenic acid analyzed using Benesi- Hilde brand approach at the wavelength of 664 nm were found to be 8418 and 14542 M-1 respectively. Thermodynamic parameters such as Gibbs free energy, enthalpy and entropy of dimerization reactions of the compounds were also investigated using Vant's Hoff equation at the temperature range of 295-301 K for self-association and 295-302 K for hetero-association. The change of enthalpy calculated for caffeine, chlorogenic acid and the complexes of MB-CAF and MBCGA at the temperature of 301 K are -12.86 ± 0.073, -14.24 ± 0.839, 5.12 ± 0.09, and 3.61 ± 0.012 kJ·mol-1, respectively. The obtained thermodynamic parameters indicated that self-and heteroassociation of the compounds are mainly electrostatic and hydrophobic interactions played a major role in the binding reactions respectively.
- Publication
Romanian Journal of Biophysics, 2017, Vol 27, Issue 2, p35
- ISSN
1220-515X
- Publication type
Academic Journal