Photo-induced reduction

Similar photo-induced reductive dissolution to that reported for lepidocrocite in the presence of citric acid has been observed for hematite (a-Fe203) in the presence of S(IV) oxyanions (42) (see Figure 3). As shown in the conceptual model of Faust and Hoffmann (42) in Figure 4, two major pathways may lead to the production of Fe(II)ag i) surface redox reactions, both photochemical and thermal (dark), involving Fe(III)-S(IV) surface complexes (reactions 3 and 4 in Figure 4), and ii) aqueous phase photochemical and thermal redox reactions (reactions 11 and 12 in Figure 4). However, the rate of hematite dissolution (reaction 5) limits the rate at which Fe(II)aq may be produced by aqueous phase pathways (reactions 11 and 12) by limiting the availability of Fe(III)aq for such reactions. The rate of total aqueous iron production (d[Fe(aq)]T/dt = d [Fe(III)aq] +... 

Faust, B. C., and M. R. Hoffmann, Photo-Induced Reductive Dissolution of -Fc20, by Bisulfite, Environ. Sci. Technol., 20, 943-948(1986). 

Compound 639 also promotes the photo induced reduction of ketones whereas 2-(2 -hydroxyphenyl)-l,3-dimethyl-benzimidazoline 640 promotes benzpinacol formation (Scheme 153) <2005JOC9632>. Photoinduced single electron transfer (SET) followed by regiospecific proton transfer (PT) led to the formation of either benzhydrol or benzpinacol, depending on the 2-aryl substituent. 

C-Cl cleavage process. Tetrachlorobenzenes in acetonitrile-water mixtures undergo photo-induced reductive dechlorination as... 

Michel and co-workers have recently dismissed the notion of a metastable state of the fully oxidised enzyme, Oh. In their experiments they produced the F state by treating the oxidised enzyme with H2O2. Subsequently, they exposed the enzyme in the F state to carbon monoxide, which is known to react with F by a strict two-electron reduction. Consequently, this procedure yields an E state without forming the metastable intermediate Oh (see Fig. 2-3). Hence, their report that photo-induced reduction of the E state produced this way (we would ascribe this state to Eh) is linked to proton translocation does not contradict our notion, but rather strengthens it. 

The radiation-chemical and photo-induced reduction is preferred to the reduction by hydrogen when it is necessary to prepare small particles with a narrow size distribution. A characteristic example is the preparation of blue silver in the process of y-irradiation of shghtly alkaline aqueous solutions of AgC104 containing 2-propanol and PAA. - The blue silver is a linear Ag cluster stabilized on a polymer molecule. In the course of radiation-chemical reduction, the Ag clusters are transformed through a number of successive stages into a polymer-immobilized colloidal silver. 

Reduction of Nitro Compounds p-Nitroacetophenone A hydroxylamine intermediate is detected by the photo-induced reduction ofp-nitroacetophenone with high yields by the irradiation of suspensions of P25 Ti02 in ethanol. The photogenerated electrons reduce the nitro compound, whereas the holes oxidize ethanol to acetaldehyde with the formation of hydrogen. 

Ogata, Y, Takagi, K., and Tanabe, Y, Photo-induced reduction of pyridinium ions catalyzed by zinc (11) tetraphenylporphyrin, /. Chem. Soc., Perkin Trans. 2, 1069,1979. 

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