Microwave technology advantages

The future of microwave technology thus lies with the identification of reactions with a potential for advantageous results vs. other means. An industrial success would undoubtedly bring microwave technology into mainstream thinking as a chemical process development tool. 

Microwaves heat the liquid phase, whereas vapors do not absorb microwave energy. The temperature of the vapor phase is therefore lower than the temperature of the liquid phase and vapor condenses on cool vessel walls. As a result, the actual vapor pressure is lower than the predicted vapor pressure. This sort of sustained dynamic, thermal non-equilibrium is a key advantage of microwave technology, because very high temperatures (and, in turn, short digestion times) can be reached at relatively low pressures. 

Physically, the paraxial approximation limits attention to beams that are not rapidly diverging. We will establish criteria for the validity of the paraxial approximation while discussing typical applications and constraints. In this way, the reader will come to appreciate the advantages and limitations of quasioptics vis-a-vis microwave technology. 

Investigation of these propositions required dedicated microwave reactors. It was essential that such systems operated reliably, safely, and routinely with volatile compounds, including organic solvents at high temperatures and at moderate pressures. To attract the attention and maintain the interest of chemists, microwave technology would need to have advantages that were unavailable with the conventional chemical process equipment of the day. 

Alkylation of malonate anion Hernandez et al. [155, 156] have developed a rapid and easy procedure for the synthesis of C-labeled esters using a combination of solvent-free phase-transfer catalysis conditions and microwave technology. A detailed study of the first step, which consists in malonic alkylation, did not reveal any advantages of microwave activation compared with conventional heating (Eq. 71) ... 

Yeh and Sun have combined the advantages of microwave technology with liquid phase combinatorial chemistry to facilitate the synthesis of thioxotetrahydropyrimi-dinones [90]. The reactions were significantly accelerated. 

The advantages of the simultaneous excitation of optical lines by laser radiation and microwave transitions to observe directly the energy difference in question are still the same optical quanta are detected with a large quantum efficiency microwave transitions exhibit a very small Doppler broadening. Without questioning the merits of all the Doppler-free laser spectroscopic methods, one should keep in mind also the enormous progress in microwave technology. 

Basically, microwave technology provides an alternative to conventional heating methods, with several important advantages penetrating radiation, controllable electric field distribution, rapid heating, selective heating of materials, and self-limiting reactions [19]. 

---