Wave guide tube

A mixture of ethyl 2-cyano-2-(l-ethoxyethylidene)aminoethanoate 2 (1 g, 5 mmol) and freshly distilled aromatic aldehyde 1 (5 mmol) was placed in a cylindrical quartz tube ( =4 cm). The tube was then introduced into a Synthe-wave R 402 Prolabo microwave reactor (2.45 GHz, adjusted power within the range 0-300 W and a wave guide (single mode TOl) fitted with a stirring device and an IR temperature detector). Microwave irradiation was carried out at 70 °C for the appropriate reaction time. The mixture was allowed to cool down. After addition of methylene chloride (15 mL) in the reactor and removal of solvent in vacuo, the crude residue was purified by chromatography on silica gel (60F 254, Merck) with the appropriate eluent. Solvent evaporation gave the desired compound 3 as a viscous oil which crystallized on standing and was characterized by NMR and HRMS analysis. 

Figure C2.13.4. Schematic illustrations of selected microwave discharges (a) the discharge tube DT is inserted through a rectangular wave guide RW parallel to the electric field, M denotes the magnetron (b) plasma reactor with slots, CP denotes the coupling probe, RC refers to the ring circulator CS to the coupling slots and Q denotes the quartz tube [22] (c) planar microwave plasma source MW, microwave and MWW, microwave window [21] ...

Rotational transitions correspond to photon wavelengths in the microwave region. The radiation sources in microwave spectrometers are klystron tubes, which were originally developed for radar apparatuses in World War II. Hollow metal wave guides carry the radiation to the sample cell, which is a hollow metal cavity, and the resonant radiation in the cavity is sampled to detect absorption. Microwave spectroscopy has played an important role in identifying molecules in interstellar space, but it is not a common tool in many chemical laboratories. 

Guided-Wave-Tube Technique for Materials Characterization... 

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