Photodegradation chemistry

MetabolExpert (302-304) is composed of databases (including animal metabolism, plant metabolism, photodegradation chemistry, and soil degradation chemistry), a knowledge-base system, and prediction tools. The biotransforma-... 

Figure 62 Photodegradation chemistry of the sulfonamide-containing brinzolamide.

Photodegradation chemistry has evolved into a highly practical state over the last few years to where commercial products are available and others are being evaluated. The degradation mechanisms are understood to the point of property loss for the plastics. The gap on environmental acceptability still needs attention, it is not sufficient to expect low molecular weight fragments to be biodegradable, this must be demonstrated. 

Antioxidants are frequently recommended as part of a multi-component package to help achieve the best possible protection against photodegradation. Chemistries include phenolics - highly efficient ABS - good FDA approval phenolic/phosphite hlends - exceptional resistance to discoloration thioesters -exceptional heat stabilization in blend/synergy with phenolics. 

Chen ZM, Zabik MJ, Eeavitt RA. 1984. Comparative study of thin film photodegradation rates for 36 pesticides. Industrial and Engineering Chemistry Product Research and Development 23 5-11. 

Topochemical [24-2] photoreactions of diolehn crystals has been reviewed. The reactions clearly depart from typical solution chemistry crystal-lattice control offers a unique synthetic route into photodegradable polymers, highly strained [24-2] paracyclophanes, stereoregular polymers, and absolute asymmetric synthesis. However, achieving the desired type of crystal... 

Wilhelm, P. and Stephan, D. (2007) Photodegradation of rhodamine B in aqueous solution via Si02 Ti02 nanospheres. Journal of Photochemistry and Photobiology A Chemistry, 185, 19-25. 

Recent studies have provided much useful information about the photodegradation of PVC, but a thorough understanding of this subject has obviously not been achieved. Many of the pertinent data are contradictory for reasons not always apparent, although it is certain that the chemistry of the process depends very strongly on reaction variables. Clearly much work remains to be done in this very important field. 

The chemistry of the oxidative and nonoxidative photodegradation of poly(vinyl chloride) is reviewed with emphasis on work that has been published since the early 1970 s. Topics covered include the nature of the photoinitiating species, the photoinitiation mechanism, and the structural consequences and reaction mechanism of the overall photodegradation process. Also included is a summary of recent studies on the determination of structural defects in poly(vinyl chloride) by carbon-13 NMR. 

Orazio, C.E. Haynes, S.A. Lebo, J.A. Meadows, J.C. Huckins, J.N. Petty, J.D. 2002, Potential for Photodegradation of Contaminants During SPMD Sampling. Presented at the 23rd Annual National Meeting of the Society of Environmental Toxicology and Chemistry November 16-20, 2002 Salt Lake City UT Abstract P192. 

Isocyanates that are produced fi om aliphatic amines are utilized in a limited range of polyurethane products, mainly in weatherable coatings and specialty applications where the yellowing and photodegradation of the aromatic polyurethanes are undesirable [5]. The aliphatic isocyanates are not used more widely in the industry due to the remarkably slow reaction kinetics of aliphatic isocyanates compared to their aromatic counterparts [6]. Due to the slow reactivity of aliphatic isocyanates, it is not practical to use them in the preparation of flexible or rigid foams, which are the main commercial applications for polyurethane chemistry. 

Similar chemistry leading to the formation of the products shown in Table 9.22 is discussed by Forstner et al. (1997b). Some of these products may accelerate the photodegradation of less reactive species in the condensed phase (e.g., McDow et al., 1996). 

AdoCbl and MeCbl are extremely susceptible to photodegradation (168). In the dark, they are relatively stable in neutral aqueous solution and can be heated for 20 minutes at 100°C. Although MeCbl is relatively stable in the presence of dilute acid or alkali, AdoCbl is unstable under acidic conditions. The chemistry of vitamin B 2 is reviewed in greater detail by Linde-mans (168). 

The copolymers of carbon monoxide with olefins are of considerable importance from several different standpoints. These include the low price and ready availability of carbon monoxide, the enhanced photodegradability of the copolymers, and their easy chemical conversion to other classes of functionalized polymers. This review summarizes the chemistry involved in the synthesis, characterization, degradation and the derivatization of the copolymers. In addition, work on the spectral characterization of the copolymers have been cited. 

Castellan, A., Colombo, N., Fomier de Violet, Nourmamode, A., and bouas-Laurent, H., "Photodegradation of Lignin A Photochemical Study of Bleached CTMP and Lignin Model Molecules", Proceedings of the 5th International Symposium of Woos and Pulping Chemistry, Raleigh, N.C., 1989, p.421-. 

Berinstain, A.B. In Singlet State Participation and Solvent Effects on the Photodegradation of a-guaiacoxyacetoveratrone, a Lignin Model Compound Concordia University, Institute for Co-operative Education, Department of Chemistry and Biochemistry Work Term Report 1990. 

Hidaka, H., J. Zhao, E. Pelizzetti and N. Serpone (1992). Photodegradation of surfactants. 8. Comparison of photocatalytic processes between anionic sodium dodecylbenzenesulfonate and cationic benzyldodecyldimethylammonium chloride on the Ti02 surface. Journal of Physical Chemistry, 96(5), 2226-2230. 

Zhao, W., C.C. Chen, X.Z. Li, J.C. Zhao, H. Hidaka and N. Serpone (2002). Photodegradation of sulforhodamine-b dye in platinized titania dispersions under visible light irradiation Influence of platinum as a functional co-catalyst. Journal of Physical Chemistry B, 106(19), 5022-5028. 

The importance of this process was not recognized until the mid-1970s when it was realized that Cl could be produced from the photodegradation of chlorofluoro-carbons (CFCs), which had become very widely used as refrigerants and for other applications for which an inert gas was needed. This realization was a big deal, and it eventually earned Mario Molina, F. Sherwood Rowland, and Paul Crutzen the Nobel Prize for chemistry in 1995. 

Bolton JR, Cater SR (1994) Homogeneous Photodegradation of Pollutants in Contaminated Water An Introduction, in Helz G R (ed.) Aquatic and Surface Chemistry, Lewis Publishers, Boca Raton 467-490. 

Bolton JR, Stefan MI, Hislop K (1995) Mechanism and Efficiencies in the Photodegradation of Organic Pollutants in Aqueous Solution, Department of Chemistry, The University of Western Ontario, London, Canada Handout of a lecture presented by Bolton at the World Environmental Congress, London, Ontario (Canada) 17-22. September (1995). 

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