Isopropanol, benzophenone-sensitized

The addition of THF to benzophenone sensitized polymerization of epoxy resin CY-179 results in a dramatically increased relative polymerization rate in the presence of lAsF, and a small increase in the presence of jy S AsF (compare Tables 1 and 2). Similarly, the addition of THF or isopropanol results in large product quantum yields ( Cp > 2) for benzophenone sensitized decomposition of -8 1 AsF, but only small increases in the decomposition of-8ls AsF ( 0.2). Quantum yields > 1... 

Abstraction of labile hydrogen atoms, for example, from tetrahydrofuran (THF), by photoexcited ketones also yields easily oxidized radicals [60a]. Quantum yields for benzophenone sensitized photolysis of diphenyliodo-nium hexafluoroarsenate in acetonitrile with hydrogen atom donors are shown in Table 9. Diaryliodonium salts are capable of oxidizing electron rich radicals from isopropanol and THF but triarylsulfonium salts are not [96]. The oxidation potential of tetrahydrofuranyl radical is —0.35 V versus SCE [109], apparently sufficient for irreversible reduction of diphenyliodonium cation ( red = approx. —0.7 V versus SCE, see above) but not of triphenyl-sulfonium cation ( red = —1.2V versus SCE). 

Pitts et al. [480] and Beckett and Porter [61, 62] found that benzophenone sensitizes the oxidation of isopropanol in accordance with the following reaction scheme. 

Backstrom and Sandros (1960) came to the same conclusion from a study of the benzophenone-sensitized emission of biacetyl in benzene or isopropanol solution. 

Irradiation of alcohols (ethanol, isopropanol, etc.) with maleic acid in the presence of benzophenone or anthraquinone as sensitizer leads to 1 1 addition products<78) ... 

A striking, but isolated, obsei vation was reported by Horner . He found that direct photolysis of benzoyl azide in ethanol or isopropanol led to the Curtius rearrangement (44%), to insertion (31%) and to some hydrogen abstraction (23%). However, in the presence of small concentrations of benzophenone the photoreaction produced exclusively benzamide, with a quantum yield far in excess of unity. The high yield indicated a chain reaction, benzophenone playing more the part of a photocatalyst than that of a convcndonal sensitizer. 

A soln. of methanesulfonyl azide in isopropanol-water irradiated 80 min. in a slow Ng-stream with a high-pressure Hg-arc lamp until gas-evolution ceases -> methane-sulfonamide. Y 99.8%. F. e., also in the presence of benzophenone as sensitizer, s. M. T. Reagan and A. Nickon, Am. Soc. 90, 4096 (1968). 

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