Product formation photooxidation

CASRN 1836-75-5 molecular formula C13H7F3N2O5 FW 284.10 Chemical/Physical. When nitrofen as an aqueous suspension was irradiated using UV light (A. = 300 nm), 2,4 -dichloro-4 -aminodiphenyl ether formed as the major products (>80% of total product formation). In addition, 4-nitrophenol and 2,4-dichlorophenol formed as minor products (<10%). In cyclohexanone, the major photooxidation product was aminonitrofen (Ruzo et al., 1980). 

Polyurethanes and Rubbers - The photooxidation of polyether-polyurethanes exhibits sensitivity due to the ether segments. Formates were the primary products of photorearrangement. The addition of styrene-butadiene copolymers to polyolefins significantly enhances their susceptibility to photooxidation via the butadiene component. Horizontal attenuated FTIR spectroscopy has been found useful for detecting the products of photooxidation of rubbers ... 

Figure 5. E ct of intensity on product formation during photooxidation ...

We have investigated the photooxidation of toluene in several different zeolite hosts (BaX, BaY, CaY, BaZSM-5, and NaZSM-5) using in-situ Fourier Transform Infrared (FT-IR) spectroscopy and ex-situ Gas Chromatography (GC) to analyze product formation and product yields. This combined approach allows for a more detailed analysis of the product distribution. The product selectivity in these reactions appears to be governed by the presence of a small number of acid sites rather than by the framework composition or topology of the zeolite host. 

The mechanism of the unsensitized photoreaction with oxygen is similar to that of photoreaction without oxygen. Both of them involve free radical or biradical formation. Photooxidation without sensitizer generally gives a more complex result than sensitizer photooxidation, probably because of co-occurrence of the photoreaction of the substrate itself, oxidation of the initial photoproduct, or further photochemical transformation of the photooxdation product (Matsuura and Saito, 1976). 

Water Treatment. Several components must be treated simultaneously in a multicomponent mixture as available in wastewaters to prove the technology of heterogeneous photocatalysis. The formation and subsequent elimination of intermediates in the photooxidative process must be monitored, identifying all intermediates and final products. 

In view of its potential for nitrosamine formation, a more detailed knowledge of the atmospheric reactions and products of UDMH is clearly desirable. In order to provide such data for UDMH and other hydrazines we have studied their dark reactions in air, with and without added O3 or NO, and have investigated their atmospheric photooxidation in the presence of NO ( 9 ). In this paper, we report the results we have obtained to date for UDMH. 

Solutions of tetrazolium salts, e.g., 53, have been reported to both become colored and bleached under the influence of both UV and visible light. Several workers have attributed this phenomenon to photoreduction to the corresponding formazan (51) and the formation of a fluorescent colorless compound (152) through photooxidation.240- 243 The reduction of 152 under UV or blue light to the intense green radical structure (153) has also been reported (Scheme 21).244 A one-electron reduction product (154) is proposed as a short-lived intermediate in the photoreduction.245... 

In the presence of nitroxide I, diisopropyl ketone photooxidation takes a course differing considerably from that without this additive (Fig. 5). In this case high yields of isobutyric acid and acetone were obtained, presumably as products arising from the postulated peroxy radicals c and d. On the other hand, the formation of isopropanol is almost completely suppressed. 

Tetrahydrofuran has been reported to exhibit an absorption maximum at 280 nm (52,56), but several workers have shown that this band is not produced by the purified solvent (30,41,57). Oxidation products from THF have been invoked in order to account for the appearance of the 280-nm band in PVC films that are solvent-cast from THF in air (57. 581. However, in some reported cases (56,59), this band was undoubtedly produced, at least in part, by a phenolic antioxidant (2.6-di-tert-butyl-p-cresol)(59) in the solvent. Since certain -alkylphenols have now been shown to be powerful photosensitizers for the dehydrochlorination of PVC (60), it is clear that antioxidant photosensitization might well have been responsible for some of the effects attributed previously (56) to THF alone. On the other hand, enhanced rates of photodegradation under air have also been observed for PVC films cast from purified THF (57), a result which has been ascribed to radical formation during the photooxidation of residual solvent (57,61). Rabek et al. (61) have shown that this photooxidation produces a-HOO-THF, a-HO-THF, and y-butyro-lactone, and they have found that the hydroperoxide product is an effective sensitizer for the photodehydrochlorination of PVC at X = 254 nm (61). 

Xiang, Y., Larsen, S.C. and Grassian, V.H. (1999). Photooxidation of 1-alkenes in zeolites a study of the factors that influence product selectivity and formation. J. Am. Chem. Soc. 121, 5063-5072... 

Besides these external processes, formation of ROS may also take place intrac-ellularly. Photooxidative stress, including UVB, stimulates various cellular processes leading to the production of superoxide radicals and hydrogen peroxide, as well as singlet-oxygen and hydroxyl radicals. The sources and production sites of ROS are mainly related to photosynthetic activities such as the pseudocyclic photophosphorylation and the Mehler reaction, which stimulate the accumulation of hydrogen peroxide (Asada 1994 Elstner 1990). 

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