Microwave chemistry

Microwave chemistry is the science of applying microwave radiation to chemical reactions. Microwaves act as high frequency electric fields and will generally heat any material containing mobile electric charges, such as polar molecules in a solvent or conducting ions in a solid. Microwave heating occurs primarily through two mechanisms: dipolar polarization and ionic conduction. Polar solvents because their dipole moments attempt to realign with the oscillating electric field, creating molecular friction and dielectric loss. The phase difference between the dipole orientation and the alternating field leads to energy dissipation as heat. Semiconducting and conducting samples heat when ions or electrons within them form an electric current and energy is lost due to the electrical resistance of the material .Commercial microwave systems typically operate at a frequency of 2.45 GHz, which allows effective energy transfer to polar molecules without quantum mechanical resonance effects. Unlike transitions between quantized rotational bands, microwave energy transfer is a collective phenomenon involving bulk material interactions rather than individual molecular excitations. Microwave heating in the laboratory began to gain wide acceptance following papers in 1986, although the use of microwave heating in chemical modification can be traced back to the 1950s. Although occasionally known by such acronyms as MAOS (microwave-assisted organic synthesis), MEC (microwave-enhanced chemistry) or MORE synthesis (microwave-organic reaction enhancement), these acronyms have had little acceptance outside a small number of groups.