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Ultrasonic Relaxation Study of the Interaction of $\beta$-Cyclodextrin with Benzoic Acid in an Aqueous Solution
New Phys.: Sae Mulli 2018; 68: 496~500
Published online April 30, 2018;
© 2018 New Physics: Sae Mulli.

Shin PARK1, Jong-Rim BAE*2

1 Division of Life and Environment, Daegu University, Gyungsan 38453, Korea
2 Department of Physics, Daegu University, Gyungsan 38453, Korea
Correspondence to:
Received December 15, 2017; Revised January 13, 2018; Accepted March 5, 2018.
cc This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Benzoic acid is an antifungal agent. In this study, we studied the interaction of $\beta$-cyclodextrin ($\beta$-CD) and non-ionized benzoic acid in an aqueous solution by using ultrasonic relaxation in the frequency range of 0.2 - 45 MHz. The interaction of $\beta$-CD with non-ionized benzoic acid showed the typical spectrum of a single relaxation process at frequencies below 1 MHz. We determined the backward rate constant ($k_b$), the equilibrium constant ($K$), and the standard volume change ($\Delta V$) of the reaction as $k_b$ = 1.81 $\times$ 10$^6$ s$^{-1}$, $K$ = 137 M$^{-1}$, and $\Delta V$ = 15.9 $\times$ 10$^{-6}$ m$^3$ mol, respectively. The backward rate constant and the thermodynamic constants were compared with those for the interaction of aspirin and 2-methoxy benzoic acid.
PACS numbers: 43.35.Fj, 43.35.Vz, 43.35.Wa
Keywords: $\beta$-CD, Benzoic acid, Inclusion complex, Ultrasonic relaxation, Rate constant, Standard volume change, Hydrophobicity

April 2018, 68 (4)
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