Microwave technology utilizes electromagnetic waves to generate heat by the oscillation of molecules upon microwave absorption. The electromagnetic spectrum for microwaves is in between infrared radiation and radiofrequencies of 30 GHz to 300 MHz, respectively, corre­sponding to wavelengths of 1cm to 1 m. Domestic and industrial microwave systems are re­quired to operate at either 12.2 cm (2.45 GHz) or 33.3 cm (900 MHz) in order not to interfere with the wavelength ranges being utilized for RADAR transmissions and telecommunica­tions [15].

In microwave-assisted heating, unlike the conventional methods, the heat is generated within the material, thus rapid heating occurs. As a result of this rapid heating, many mi­crowave-assisted organic reactions are accelerated, incomparable with those obtained us­ing the conventional methods. Thus, higher yields and selectivity of target compounds can be obtained at shorter reaction times. In addition, many reactions not possible using the conventional heating methods, had been reported to occur under microwave heating. Some very useful information on the fundamentals of microwave-enhanced chemistry, its sam­ple preparation and applications are well presented in the book edited by Kingston and Haswell [16].

Other than the above mentioned advantages of rapid, internal and selective heating, micro­wave non-thermal effects on reaction likely occur, obtaining dramatic increase in the yield even at milder conditions. The microwave non-thermal effect is defined as the system re­sponse to electromagnetic energy not attributed to temperature variation [17]. Although doubts are cast on the true existence of non-thermal effects, some evidences had been re­ported and postulates had also been made by several researchers. These were summarized in a review article published by de la Hoz et al [18] comparing them with the thermal ef­fects. The review of Jacob et al [19] on thermal and non-thermal interaction of microwaves with materials attributed some interesting results on specific microwave effects. Evidences on reaction rate enhancement due to some reasons other than the thermal effects such as "hotspots" or localized heating, molecular agitation, improved transport properties were discussed. They suggesed that due to the interaction of microwave with the materials, heat­ing cannot be simply treated as that similar to the conventional methods as there are a lot of possible mechanisms of activation of materials that might possibly occur.