Dr.Nadia Sadiq Majeed
Department of Chemistry
In organic chemistry, one of the very current styles is microwave-assisted organic synthesis (MAOS). Many types of organic reaction examined successfully in microwaves (MWs) for preparation of heterocyclic compounds, pharmaceutical, carbon material, solid-phase peptide synthesis and nanoparticles because reduction of reaction time for days and hours to minutes and seconds, improvement of the purification and development of product yield, all these reasons increase to money and time saving and useful to the environment.
The first microwave oven was presented in 1955 by Tappan but the common use of microwave ovens happened through the 1970 and 1980 while the first application of microwave irradiation in 1986 used for chemical synthesis.
A microwave (MWI) is a form of electromagnetic energy, the two mechanism for transferring energy from microwave to the material are ionic conduction and dipole rotation therefore only polar molecules transfer energy rapidly and absorb microwave irradiation very well but non-polar molecules are inert to microwave dielectric loss, also the boiling point values when solvents are used in microwave irradiation conditions are higher than with conventional heating . This effect, called the ” super heating effect”’ There are two general classes of microwave effects in organic chemistry :
Specific microwave effects are those effects that cannot be easily emulated through conventional heating methods such as :
Rapid heating rates and temperature gradients.
The elimination of wall effects.
Selective heating of specific reaction components.
Non-thermal microwave effects have been proposed in order to explain unusual observations in microwave chemistry as the name suggests, the effects are supposed not to be require the transfer of microwave energy in to thermal energy.