Microwave apparatus

Thiophenes of type 31 (X-Y = CH) were generated via Lawesson s reagent-mediated cyclization of 1,4-dicarbonyl compounds 30 under microwave irradiation in the absence of solvent [37]. The reaction was carried by mixing the two solid reagents in a glass tube inserted inside a household microwave apparatus and irradiating until the evolution of H2S ceased. An interesting application of this method is the preparation of liquid crystals and other ferro- and antiferroelectric material such as compound 33 (Scheme 10). 

The pyrrolidines were obtained in a two-step, one-pot reaction in good yields and short reaction time (5 min vs. 36 h reported for the conventional heating) [73], using a single-mode microwave apparatus [74]. 

Fig. 2 Synthos 3000 bench-top multimode microwave apparatus of Anton Paar...

Methyl umbelliferone, pH-dependent change of fluorescence 91 Metoxurone 74 Mevinphos (cis/trans) 362 Microwave apparatus 96 ff Mirsol 45... 

Figure 3.17 Microwave apparatus (Soxwave 100, Prolabo, France). After Letellier etal. [472]. Reprinted with permission from LC.GC International, Vol. 12, Number 4, April 1999, pp. 222-225. LC.GC International is a copyrighted publication of...

Figure 28-10 Microwave apparatus for digesting organic materials by wet ashing. [Courtesy Spex Industries, Edison, NJ.J...

Microwave Heating The same mixture as before was introduced in the quartz reactor of the microwave apparatus, surmounted by the same Dean-Stark condenser. Microwave irradiation was programmed using the computer for a sequential process in which the sample was exposed for periods of 2 min separated by periods of 2 min. This sequence was repeated 6 times with an incident power of 90 W for the first two irradiations and of 75 W for the others. After the mixture cooled, the same treatment as before gave a 90% yield in 2c. 

The excellent insulating and dielectric properties of BN combined with the high thermal conductivity make this material suitable for a huge variety of applications in the electronic industry [142]. BN is used as substrate for semiconductor parts, as windows in microwave apparatus, as insulator layers for MISFET semiconductors, for optical and magneto-optical recording media, and for optical disc memories. BN is often used as a boron dopant source for semiconductors. Electrochemical applications include the use as a carrier material for catalysts in fuel cells, electrodes in molten salt fuel cells, seals in batteries, and BN coated membranes in electrolysis cells for manufacture of rare earth metals [143-145]. 

In general, organic extraction and acid digestion use different types of microwave apparatus, as these two processes require different reagents and different experimental conditions. A new commercial system, Mars X (CEM Corp., Matthews, NC) offers a duel unit that can perform both proce-... 

Safety features are essential to a microwave apparatus. An exhaust fan draws the air from the oven to a solvent vapor detector. Should solvent vapors be detected, the magnetron is shut off automatically while the fan keeps running. Each vessel has a rupture membrane that breaks if the pressure in the vessel exceeds the preset limit. In the case of a membrane rupture, solvent vapor escapes into an expansion chamber, which is connected to the vessels through vent tubing. To prevent excessive pressure buildup, some manufacturer use resealable vessels. A spring device allows the vessel to open and close quickly, releasing the excess pressure. 

The authors irradiated a sample of Sceptrin in water at 195 °C for 1 min, using a dedicated monomode microwave apparatus. They investigated the process in detail and found that after a series of tandem tautomerizations and [1,2] shifts, Scerptin did indeed convert into the structural analogue Ageliferin. They further confirmed the reaction and mechanistic details by deuterium-labeling. 

Szepesy et al. used a microwave apparatus in the determination of acetylcholine and choline in the central nervous system samples [221]. Schmidt et al. reported the use of a microwave radiation method for the determination of acetylcholine in the rat brain [222]. 

Apparatus For sample digestion, use the microwave apparatus as described for Apparatus in the Arsenic test (above). For sample analysis, see Apparatus for Method I in the Atomic Absorption Spectrophotometric Graphite Furnace Method under Lead Limit Test, Appendix IIIB. 

Apparatus For sample digestion, use the microwave apparatus as described for Apparatus in the Arsenic test (above). 

Naphthol (0.35 mmol) was dissolved in 2 ml l-ethyl-3-methylimidazolium tetrafluoroborate containing benzyl bromide (1.5 eq) and KOH (2eq). The mixture was reacted in a microwave apparatus at 200°C 2 minutes, the product extracted with diethyl ether, and isolated in quantitative yield. 

Microwave radiation used in these alkylations had a frequency range of between 500 MHz and 100 GHz, available in most commercial microwave units. A typical microwave apparatus is described (1). 

Although all measures have been taken by microwave apparatus manufacturers to make microwave a safe source of heating in chemical reactions, uncontrolled reaction conditions may lead to undesirable results such as excessive heating of volatile reactants may result in explosive conditions. The improper use of... 

The user must pre-inquire about the basic parameters of microwave apparatus being used, which may include the model no., year of manufacturing, serial no.,... 

Figure 21. Schematic diagram of microwave apparatus for investigating W/O...

Microwaves are electromagnetic waves with frequencies between 30 GHz and 0.3 GHz, corresponding to wavelengths from 1cm to lm. To avoid interference with radar and telecommunications, industrial and domestic microwave apparatus may only operate at wavelengths regulated at both national and international levels. In the majority of countries,... 

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