Academic Institution: University of District of Columbia
Academic Standing as of September ’09: Graduate
Project: The application of microwave energy in organic chemistry is increasing rapidly. Microwave-assisted synthesis, for example, has proven to enhance many chemical processes in term of reaction rate and energy consumption. Microwave radiation in the electromagnetic region corresponds to wavelengths of 1 cm to 1 m (frequencies of 30 GHz to 300 GHz respectively).When exposed to microwave frequencies; the dipoles of the sample align themselves with in the applied electric field. As the field oscillates the dipole field attempts to realigns itself with the alternating electric field and, in the process, energy in the form of heat is lost through molecular friction and dielectric loss causing the well known thermal effect of microwaves. In the past few years however, there have been a mentioning of other microwave effects such “specific” and “non-thermal” that some think may contribute to the overall enhancement observed in microwave-assisted chemical synthesis or processes. Such effects have been claimed when the outcome of a synthesis preformed under microwave condition was different from the outcome of the same reaction performed under conventional conditions at the same measured reaction temperature. These claims have created a lot of controversy as to whether athermal- non Arrhenius effects do in fact occur under microwave conditions.
This experiment aims to use microwave irradiation (8-18 GHz, 50 W) to assist the esterification of benzoic acid with ethanol under reflux conditions. This reaction is carried by using a catalyst (sulfuric acid) and a heat source to keep the reaction at temperatures between 70 and 80 ° C. Ethyl benzoate and water are the products of this type of esterification. Our experimental set up includes a sophisticated microwave oven and a (50 W) amplifier with a waveguide used to deliver microwave energy to glass tubing inserted into an opening on the waveguide. A thermocouple of type T (copper/Constantine) is used to provide temperature feed-back from the sample in the glass tubing to a computer programmed to control the power of the microwave generator.
The goal of this study is to compare the esterification reaction rate when carried out under microwave and conventional conditions at the same measured reaction time and temperature. The control experiment will be set up to heat the reaction conventionally (water bath) under reflux conditions. The effect of microwave energy absorption on the reaction rate of ethanol and benzoic acid will be measured as a function of frequency and power level.