Degradation studies photochemistry

Photochemistry of Model Compounds. Preliminary photochemical studies have been carried out on l,3-diphenoxy-2-propanol (3)8 as a model compound for bisphenol A-epichloro-hydrin condensates 1. The utilization of 3 as a model compound for thermal degradation of 1 has been reported. Irradiation (254 nm) of 3 in acetonitrile (N2 purge) provides two major volatile products, which have been identified as phenol and phenoxyacetone (4), by comparison of retention times (gas chromatography) with known samples. A possible mechanism for... 

Kusic, H, Koprivanac, N Srsan, L. Azo dye degradation using Fenton type processes assisted by UV irradiation A kinetic study. Journal of Photochemistry and Photobiology A Chemistry, 2006 181 (2-3), 195-202. 

Guillet and coworkers have carried out extensive studies on the photochemistry of the QH4—CO copolymer 53-55). The absorption of light in the near-UV region by the copolymer resulted in a decrease in molecular weight, accompanied by the evolution of CO. In addition, the IR spectrum of the degraded polymer exhibited... 

Castellan, A., Vanucci, C., Bous-Laurent, H., "Photochemical Degradation of Lignin Through a C-0 Bond Cleavage of Non-phenolic Benzyl Aryl Ether Units. A Study of the Photochemistry of a(2 ,4 -Trimethyl-Phenoxy)-3,4 Dimethoxy Toluene.", Hohforschmg, 1987, 41(4), 231. 

Ghosh and co-workers have shown in several studies that Brij 35 and Pol 10 in water provide suitable environments for the photochemically induced reductive dechlorination of chlorobiphenyls [75,77,82,83]. Ghosh and Sayler have demonstrated that photochemistry and microbes work symbiotically to degrade PCB mixtures [76,80]. Photochemistry in a surfactant/water solution converts highly chlorinated biphenyls into much less chlorinated ones. The microbes, which do not oxidize the highly chlorinated biphenyls, then oxidize the less chlorinated biphenyls. For a related study on the combined degradation of a PCB mixture and microbes see [88]. 

We focus initially on the photochemical behaviour of complexes of Fe(III) with simple carboxylic acids and give particular attention to oxalic acid. This compound is prevalent in atmospheric aerosols [28], provides a simple example of environmentally important light-mediated ligand-to-metal charge transfer (LMCT) processes which result in ligand decarboxylation [27] and is used to initiate the degradation of contaminants both in the absence and presence of added hydrogen peroxide (via the so-called modified photo-Fenton process [29,30]). In addition, the photochemistry of Fe(III)-oxalate complexes has been studied in detail, as it is the basis of... 

Degradation of Larger Silicon Catenates. Although it seems clear that polymeric disilane derivatives photodecompose by bond homolysis to produce silyl radicals, model studies on larger silicon catenates indicate that their photochemistry may be more complex (Scheme IV). Cyclic silane derivatives seem to extrude monomeric silylenes upon irradiation to produce smaller cyclic silanes (52). The proposed silylene intermediates have been identified spectroscopically 49, 53), and trapping adducts have been isolated in solution. Exhaustive irradiation ultimately results in acyclic silanes, which... 

Solutions were exposed to 20 Whr/m or 40 Whr/m of UV light in a ICH photochamber and analyzed by HPLC. The amount of drug loss observed for the formulations is significant and ranges from 3.2% to 17.1% label claim (Table 14). The results of this study indicate that media and drug structure may affect the degradation rate but that the underlying photochemistry is likely widely applicable. 

In heterogeneous photochemistry, an increasing effort is going into the study of the photocatalytic degradation of organic pollutants with Ti02 as a photocatalyst. In these oxidation processes either the organic compound is directly oxidized by the valence band holes (hvli+)... 

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