Microwave chemistry is the science of applying microwave irradiation to chemical reactions ^{[1] [2] [3]}. Microwaves act as high frequency electric fields and will generally heat anything with a mobile electric charge. Polar solvents are heated as their component molecules are forced to rotate with the field and lose energy in collisions. 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. Heating a reaction or chemical reactor by microwave radiation (as seen in a domestic microwave oven) has a number of advantages over conventional heating; Microwave image of 3C353 galaxy at 8. ... In physics, an electric field or E-field is an effect produced by an electric charge (or a time-varying magnetic field) that exerts a force on charged objects in the field. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interactions. ... A substance is soluble in a fluid if it dissolves in the fluid. ... Electric current is the flow of electric charge. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Chemical reactors are vessels that are designed for a chemical reaction to occur inside of them. ... Microwave oven A microwave oven, or microwave, is a kitchen appliance employing microwave radiation primarily to cook or heat food. ...

• The heat is formed directly and rapidly in the sample.
• Energy is not wasted in heating furnaces or oil baths.
• The entire volume of the reactor can be heated (virtually) uniformly.
• Selected volumes of the sample (including microscopic regions) can be selectively heated.

Conventional heating usually involves the use of a furnace or oil bath, which heats the walls of the reactor by convection or conduction. The core of the sample takes much longer to achieve the target temperature (Particularly when heating a large sample of ceramic bricks, for example. Rapid and homogeneous heating has the following benefits: Look up Homogeneous in Wiktionary, the free dictionary. ...

• reaction rate acceleration
• milder reaction conditions
• higher chemical yield
• lower energy usage

Some of these effects are derived from superheating or hot spots, well known effects in microwaving. The reaction rate for a reactant or product in a particular reaction is defined as the amount of the chemical that is formed or removed (in moles or mass units) per unit time per unit volume. ... Yield in chemistry, also known as chemical yield and reaction yield, is the amount of product obtained in a chemical reaction. ... In physics, superheating (sometimes referred to as boiling retardation, boiling delay, or defervescence) is the phenomenon in which a liquid is heated to a temperature higher than its standard boiling point, without actually boiling. ... It has been suggested that this article or section be merged with microwave oven. ...

Selective heating is particularly important in the microwave heating of supported metal catalysts. A specific application in synthetic chemistry is in the microwave heating of a binary system comprising a polar solvent and an apolar solvent obtain different temperatures. Applied in a phase transfer reaction a water phase reaches a temperature of 100°C while a chloroform phase would retain a temperature of 50°C. Microwave chemistry is particularly effective in dry media reactions. A catalyst (Greek: καταλύτης) is a substance that accelerates the rate of a chemical reaction, at some temperature, but without itself being transformed or consumed by the reaction (see also catalysis). ... A commonly-used example of a polar compound is water (H2O). ... A phase transfer catalyst or PTC in chemistry is a type of chemical compound, often a quaternary ammonium salt, which facilitates the migration of a particular chemical component in one phase into a other phase in a heterogeneous system. ... PEL-TWA (OSHA) 50 ppm (240 mg/m3) IDLH (NIOSH) 500 ppm Flash point non-flammable RTECS number FS9100000 Supplementary data page Structure & properties n, εr, etc. ... A dry media reaction or solid-state reaction is a chemical reaction system in the absence of a solvent. ...

See also

Microwave effect The phrase microwave effect is a term that is actually applied to a range of observations in microwave chemistry. ...

Non-thermal microwave effect Non-thermal microwave effects have been posited in order to explain unusual observations in microwave chemistry. ...

References

1. ↑  Microwaves in organic synthesis. Thermal and non-thermal microwave effects, Antonio de la Hoz, Angel Diaz-Ortiz, Andres Moreno, Chem. Soc. Rev., 2005, 164-178
2. ↑  Developments in Microwave-assisted Organic Chemistry. C. Strauss, R. Trainor. Aust. J. Chem., 48 1665 (1995).
3. ↑  Dry media reactions M. Kidwai Pure Appl. Chem., Vol. 73, No. 1, pp. 147–151, 2001. [4]

External links

• AMPERE (Association for Microwave Power in Europe for Research and Education)
• Microwave Chemistry Pages --> Comprehensive introduction to "microwave chemistry"
• MAOS (Microwave-Assisted Organic Synthesis) --> General web resource guide of "microwave chemistry"
• Microwave Synthesis @ organic-chemistry.org

Instrument suppliers homepages

• Biotage AB
• CEM
• Anton Paar
• Milestone