Photochemical irradiation apparatus

Fig. 14.4 Apparatus for electrodeless photochemical irradiation. A. antenna, B. transmitter, C-j. capacitor, C2. variable capacitor,...

According to ref. 3, nonacarbonyldiiron [Fe2(CO)g] was synthesized by photochemical dimerization of pentacarbonyliron [Fe(CO)s] in a mixture of glacial acetic acid and acetic acid anhydride (10 1) at room temperature employing a Dema irradiation apparatus with a Philips HPK 125 W or TQ 150 W medium pressure mercury lamp. The material should be stored at -25°C in a freezer and handled under an atmosphere of argon. Pentacarbonyliron [Fe(CO)s] was a gift from BASF AG, Germany and was used without further purification. 

Fig. 1. Irradiation apparatus for photochemical reactions in which a precipitate is formed [after 202,285)]...

Although photochemical cycloadditions have gained acceptance in synthetic chemistry, most such reactions are limited to a relatively small scale. The use of a 1000-watt street lamp permits the irradiation of up to 1 mol of substrate in less time than 0.2 mol can be irradiated with the conventional 450-watt lamps. Thus, under optimum conditions, the submitters were able to add ethylene to 3-methylcyclohexenone on a 20-g scale in 48 hr (801) with a 450-watt lamp with the apparatus described here 94 g of this enone was condensed with ethylene in 8 hr (91%). 

The apparatus and techniques of ion cyclotron resonance spectroscopy have been described in detail elsewhere. Ions are formed, either by electron impact from a volatile precursor, or by laser evaporation and ionization of a solid metal target (14), and allowed to interact with neutral reactants. Freiser and co-workers have refined this experimental methodology with the use of elegant collision induced dissociation experiments for reactant preparation and the selective introduction of neutral reactants using pulsed gas valves (15). Irradiation of the ions with either lasers or conventional light sources during selected portions of the trapped ion cycle makes it possible to study ion photochemical processes... 

Typical configurations of laser flash photochemical apparatus for the detection of transients in a timescale longer than 1 ns are shown in Figure 6.8. The pump-probe configurations in Figure 6.8 are used for the front-face and side-on irradiations of the... 

Hazards. Eyes and skin can be severely injured by ultraviolet radiation. One should avoid looking at the reaction mixture when the irradiation source is activated. The photochemical apparatus, especially when using immersion set-ups, must be wrapped appropriately to avoid exposure to the ultraviolet radiation. In view of the high temperatures produced by the lamp, efficient cooling is mandatory. Special care must be exercised when flammable solvents are used. Ozone is also produced, so that working in an efficient hood is essential. Furthermore, proper electrical safety is necessary to avoid high voltage shocks. 

Luminous intensity-time curves and spectra of test samples stimulated thermally and photochemically were measured with a chemiluminescence spectrometer CLA-FSl. Colour photos of the photoluminescence of samples placed in a cell with a diameter of 50 mm were taken with the Cube-2DI, which is employing an ultra high sensitive colour CCD camera of Bitran Co., Japan. Both types of the apparatus are available from the Tohoku Electronic Industrial Co., Japan. The black light has power of 240 aW cm" and wavelength of 365 nm. In order to obtain a spectrum for steep decay photoluminescence curves, a sample was irradiated with the NUV light for 5 sec... 

Small (1-5 g) scale UV photolysis of air sensitive compounds can be performed in quartz Schlenk tubes, or in conventional Schlenkware with the use of a UV transparent quartz stopper. The latter apparatus is easily adapted to low temperature irradiations. Large scale (10-50 g) UV photochemical reactions use quartz immersion well reactors. Medium pressure Hg-arc lamps are the preferred radiation sources for synthetic applications. ... 

This modular apparatus allows even very special applications. As a further example a combined measurement and irradiation device can be set up where the sample is placed in a Dewar and kept at low temperature. Fast shutters, a beam splitter, and a repositioning device for sample and reference allow the uninterrupted examination of photochemical reactions under specific conditions (see Fig. 4.12) [54]. 

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