![]() Get help with access Institutional accessĪccess to content on Oxford Academic is often provided through institutional subscriptions and purchases. However, the charge effect on a carboxylic group on the parameters was determined to contribute significantly to stability of the complexes formed by the acids and β-CD and to the rate constants for the departure of the acids from β-CD cavity. It was found that the substituent effect on the rate and thermodynamic parameters was not remarkable in the dissociated forms of the ortho-substituted benzoic acid. The results were compared with those in solution containing aspirin and β-CD. ![]() The forward and backward rate constants, the equilibrium constants and the standard volume changes for the host–guest complexation reaction were determined from the acid concentration dependences of the relaxation frequency and the maximum absorption per wavelength. From the concentration dependence of the parameters, the cause of the relaxation was attributed to a perturbation of an equilibrium associated with an inclusion complex formed by the host and the guest. Ultrasonic relaxation parameters were determined as a function of the guest concentration. A single relaxational absorption was found when the host and the guest were coexisting in water. The dynamic interactions between β-cyclodextrin (β-CD) (host) and salicylic acid (guest) at pH ≈6 and ≈3 and between β-CD and benzoic acid (guest) at pH ≈6 were investigated in aqueous solutions in terms of ultrasonic absorption in the frequency range from 0.8 to 95 MHz.
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