A broad range of research on chemical reactions by microwave heating has been conducted, because unlike reactions by conventional heating, reactions by microwave heating underwent a reaction acceleration phenomenon. The microwave effect on chemical reactions has been previously discussed as a thermal or non-thermal effect without universal knowledge. Measuring temperature accurately is essential for discussing reaction kinetics such as reaction acceleration, however, it is difficult to measure temperature distribution accurately in a microwave reaction vessel. This mini- review introduces recent researches on the measurements of temperature distributions in microwave reaction vessels using multiple fluorescent fiber optic thermometers, and also proposes precautions on how to measure temperatures for microwave-assisted chemical reactions. Furthermore, this mini- review presents a new thermometer for measuring local heating by microwave irradiation.
Keywords: Microwave, fiber optic thermometer, infrared thermometer, Raman spectroscopy, Microwave organic synthesis, Frequency effect, 5.8 GHz, Ionic liquid, Suzuki-Miyaura coupling reaction, microwave organic synthesis apparatus, Diels-Alder reaction