New instrumentation for the comprehension of chemical reactions under microwave and classical heating with the aid of a wide frequency band dielectric spectroscopy

An instrumentation system for measuring wide frequency band complex permitt ivity of a sample submitted to a microwave irradiation has been optimized i n order to allow macroscopic temperature measurements. The reaction of sapo nification of aromatic esters is studied using this instrumentation. We tak e interest in the behavior of the ionic conductivity phenomenon occurring i n the reactive medium during microwave heating, and we compare it with the results obtained under classical heating. We show that the activation energ y associated with ionic conductivity is lower when the reaction is performe d under microwaves than when it is performed under classical heating. We th us deduce that microwaves act on the reaction advancement as a catalyst, an d thus makes the reaction easier.