Isothermal kinetics of C60 polyhydroxylation in a two-phase system in the presence of tetrabutylammonium hydroxide

Abstract

The isothermal kinetics of fullerene (C60) polyhydroxylation with sodium hydroxide in the presence of phase-transfer catalyst tetrabutylammonium hydroxide (TBAH) in a two-phase system was investigated. A spectrophotometric method for the determination of the degree of C60 polyhydroxylation was developed. The isothermal kinetic curves of C60 polyhydroxylation were measured in the temperature range from 300 to 328 K. The dependence of effective activation energy on the degree of polyhydroxylation was calculated by using the isoconversional method. The kinetics of polyhydroxylation is mathematically described successfully with the kinetic model of first order chemical reaction. The values of the rate constants, activation energy and pre-exponential factor of polyhydroxylation were calculated. The thermodynamic parameters of activated complex formation for C60 polyhydroxylation [standard enthalpy of activation (∆H*), standard entropy of activation (∆S*) and standard free Gibbs energy of activation (∆G*)] were calculated by using Eyring equation. The effect of stirring speed on the reaction rate constants of polyhydroxylation in the presence of the two types of phase transfer catalysts, TBAH and cetyltrimethylammonium bromide (CTAB) was determined. The reaction mechanism of phase-transfer catalyst and activation of C60 molecule for the reaction of polyhydroxylation was suggested.