Effect of Microwave Radiation on the Acetate-Catalyzed Hydrolysis of Phenyl Acetate at 25 °C

Abstract

In this paper we present the experimental results obtained from phenyl acetate hydrolysis in a microwave-irradiated environment and in water solutions containing catalytic acetate ions. The kinetics of the reaction were studied in an irradiated environment where radiation, at a frequency of 2.45 GHz, was given to the reacting system at a power of 0.500 ± 0.025 W. The energy absorbed by the reacting system was measured using a directional coupler, which can separate the radiation directed to the reactor from any reflected one. The system was irradiated with a power greater than that required to run the reaction; however, any energy in excess of that absorbed by the reaction was quite easily taken up by a thermostatic system. In this way the reaction system could run without any thermal effect due to radiation. The temperature was set at 25 °C and was kept constant during the reaction by using carbon tetrachloride as the thermostating fluid. The results obtained show that the kinetics of the reaction studied were greatly enhanced with respect to those of the reaction running in a nonirradiated environment. The kinetic constant at zero concentration of the catalytic species rises from 1.92 × 10-4 h-1 in a nonirradiated environment to the value 27.58 × 10-4 h-1 found here. The observed kinetic constant retains the same value for all of the studied catalytic acetate ion concentrations. This fact suggests that microwave radiation produces something like a catalytic effect which can replace that given by acetate ions in nonirradiated environments.

Microwave material processing—a review

“…It was found that at 25 C, a substantial increase in reaction rate was observed in the microwave environment than in nonradiated environment. 261 But at 35 C, the kinetic constant was found to increase 16 fold from a nonradiated environment to an environment radiated with a microwave of 50 mW. As a result, the activation energy was reduced, illustrating the athermal effect of microwave.…”

Effect of temperature and microwave power on the hydrolysis of phenyl acetate

“…We have already presented a study to the scientific world in which we demonstrated at a constant temperature of 25°C, a modest increase in the reaction rate of phenyl acetate hydrolysis running in a radiated environment with respect to that running in a nonradiated environment (Carta, 2002). In the same work, we suggested the possibility that the increase could be attributed to a sort of catalytic effect of the microwave radiation.…”

“…The radiating apparatus was presented in a previous work by the same authors (Carta, 2002). Particular attention was paid to the design of the reactor.…”

“…The values of the optical density were read every 10 min. The procedure and the experimental apparatus are better described in a previous work by Carta and Loddo (2002). The data reported were obtained by averaging the three values read at intervals of 30 s; these three values were taken as being obtained at the same time because the reaction rate was very small.…”

“…The concentration of PA used in all the reacting solutions was so high that any fractional errors were small enough so as to not affect the results, although the maximum value reported by Carta (2002) was respected. Because of this, the given optical densities were in the interval 0.24 -0.50.…”