Dilute alcoholic solutions irradiation

The irradiation of dilute alcoholic solutions produces mainly solvated electrons and solvent radicals with no direct action on the solute. The solvent radicals may be initially positive ions ROH which will convert very rapidly into carbon centered radicals. For example, in 2-propanol the main radicals will be (CH3)2Coh. a small amount of acid, ROhJ, is also produced. 

The metals, and to a lesser extent Ca, Sr, Ba, Eu, and Yb, are soluble in liquid ammonia and certain other solvents, giving solutions that are blue when dilute. These solutions conduct electricity electrolytically and measurements of transport numbers suggest that the main current carrier, which has an extraordinarily high mobility, is the solvated electron. Solvated electrons are also formed in aqueous or other polar media by photolysis, radiolysis with ionizing radiations such as X rays, electrolysis, and probably some chemical reactions. The high reactivity of the electron and its short lifetime (in 0.75 M HC104, 6 x 10"11 s in neutral water, tm ca. 10-4 s) make detection of such low concentrations difficult. Electrons can also be trapped in ionic lattices or in frozen water or alcohol when irradiated and again blue colors are observed. In very pure liquid ammonia, the lifetime of the... 

Upon ultraviolet irradiation of 4,4-dialkylated 2-cyclohexenones in dilute butyl alcohol solution, bimolecular photoreactions (reductions, solvent additions, dimerizations) are largely suppressed and... 

This disadvantage has now been overcome by generating the radicals in the liquid state in a flow system. Two techniques have been used. In one, a very dilute solution of hydrogen peroxide in the alcohol is irradiated while it flows through the cavity (Livingston and Zeldes, 1966). In the second, the hydroxyl radical is generated by the inter-... 

Procedure Weigh accurately about 20 mg of stilbosterol in sufficient ethyl alcohol to produce 100 ml and dilute 10 ml of this solution to 100 ml with ethyl alcohol. To 25 ml of the resulting solution add 25 ml of dispotassium hydrogen phosphate solution, transfer a portion of the mixture to a 1-cm closed quartz cell, place the cell 10 cm from a 15 watt short-wave UV-lamp, and subject it to irradiation for 10 minutes. Now, measure the extinction of the irradiated solution at the maximum at about 418 nm as described earlier. 

Diphenyl ether undergoes cleavage on ultraviolet irradiation in alcoholic solvents,but irradiation of dilute solutions in cyclohexane in the presence of an equimolar amount of iodine as oxidant produces dibenzo-furan As in heteroatom-directed photoarylations, a conrotatory elec-trocyclization producing the carbonyl ylide intermediate 40 (Scheme 1) is... 

A solution of 0.01 mole terhbuty] peroxide (p. 114) in excess ethylbenzene was irradiated with ultraviolet light for several hours. Gas chromatographic analysis of the product showed the presence of nearly 0.02 mole of /er/-butyl alcohol. Evaporation of the alcohol and unreacted ethylbenzene left a solid residue which was separated by chromatography into just two products X (1 g) and Y (1 g). X and Y each had the empirical formula CgH9 and m.w. 210 each was inert toward cold dilute KMn04 and toward Brj/CCU. 

Using a lead cathode in dilute methanolic sulfuric acid at constant current of 20 mAmp cm-2, the benzyl alcohol was the major product from an unstirred solution, while mechanical stirring reversed the position to favor the hydrodimer. However, ultrasonic irradiation from a cleaning bath (100 W, 36 kHz) so strongly favored the hydrodimer that the alcohol was barely evident. The effect varied somewhat with the position of the cell in the ultrasonic bath, and increased in magnitude with ultrasonic power, but throughout all electrolyses there was no appreciable change in the stereochemistry (dl/meso ratio) of the benzoin hydrodimer. 

When the monomer is irradiated in a solvent such as water or alcohol, the radical or ionic intermediates formed from both the monomer and the solvent may initiate polymerization. The yield of initiating particles, to a first approximation, is expected to be proportional to the sum of the yields of intermediates in the irradiation of pure monomer or solvent, respectively, multiplied by their electron fractions (linear mixing rule, see O Eqs. (23.3) and (O 23.4) in O Sect. 23.3.1). In practice, however, the yield of initiation may be lower or higher than it is expected assuming linearity. This is due to energy or charge transfer between the components of the mixture. In dilute solutions (e.g., in water) it is commonly assumed that initiation occurs only by the intermediates of the solvent decomposition. 

Hydroxycyclopentenones related to 8 and 9 are obtained by irradiation of dilute aqueous acetic acid solutions of dienones with a medium- or high-pressure mercury lamp in a quartz reactor or screened by a Pyrex filter. Acetoxy or alkoxy ketones are obtained under these conditions using acetic acid or alcohols (or alcoholic acetic acid), respectively, as the solvent. However, deviations from this general trend are possible, depending on the nature of the substituents in or around the chromophore. 

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