Structure/degradation relationships

Cantier, J.M., J. Bastide, and C. Coste. 1986. Structure-degradability relationships for propyzamide analogues in soils. Pestic. Sci. 17 235-241... 

Abstract Over 30 000 chemicals are used in commercial quanhhes and very few of these chemicals have experimental data on their environmental degradability/persistence. This chapter reviews databases which can be searched for persistence informahon and what to do when the chemical of interest does not have any data. Two general approaches are suggested (1) identify chemicals that are similar in structme and have persistence data or (2) use general quantitative structure-degradation relationships (QSDR) models. It is concluded that estimation methods are available for the most important degradation processes atmospheric oxidation, biodegradation, and hydrolysis. 

Keywords Biodegradation Persistence prediction Structure/degradability relationships... 

Scheme 2.7 Structure/degradation relationship for alkylbenzene sulfonates...

Further research is directed to the determination of the fine-structure of the pectins and hemicelluloses isolated from soy meal, using chromatography and degradation with specific enzymes. With these results a model of the polysaccharides present in the cell wall of soy will be formulated. Furthermore, application directed experiments will be performed to obtain information about structure-function relationships. 

Torres RA, Torres W, Peringer P, Pulgarin C (2003) Electrochemical degradation of p-substituted phenols of industrial interest on Pt electrodes. Attempt of a structure-reactivity relationship assessment. Chemosphere 50 97-104... 

Extensive biochemical and spectroscopic studies have been undertaken on hCP in order to investigate the nature of the copper centers and their role in structure-function relationships. However, the protein is very susceptible to aggregation, proteolysis, loss of copper, and other chemical degradations and requires careful preparation and handling in these circumstances it is difficult to review all the literature objectively and comprehensively. A three-dimensional crystal structure of hCP has been reported at a nominal resolution of 3.1A [7], but this resolution has been extended to just beyond 3.0 A. This chapter will summarize some of the more important biochemical and spectroscopic studies of the protein. It will then focus on the structural results recently obtained by X-ray crystallographic methods and attempt to explain putative functions of the protein in terms of its molecular structure. 

Figure 8.1 Environmental degradation scheme tor tributyltin and triphenyltin compounds. (Modified from Smith, P.J. 1978b. Structure/Activity Relationships for Di- and Triorganotin Compounds. I.T.R.I. Rep. 569. 16 pp. Avail, from International Tin Research Institute, Greenford, Middlesex, U.K. and Eisler, R. 1989. Tin hazards to fish, wildlife, and invertebrates a synoptic review. U.S. Fish Wildl. Serv. Biol. Rep. 85(1.15). 83 pp.

Physical Properties, Transport and Degradation of Environmental Fate and Exposure Assessments, Quantitative Structure-Activity Relationships in Environmental Sciences, VII, Chapter 13, SETAC Press, USA. 

The rate of acid-catalyzed degradation of the penicillins also depends largely on the nature of their acylamido side chain. Structure-activity-relationship studies undertaken for the rational design of orally active penicillins have shown that the stability in gastric juice increases with the sum of Taft s inductive substituent constants (of values) of the 6-amino side chain [95]. 

Understanding of the mechanism of radiation degradation of polymer molecules is essential for development of improved and new industrial processes, for radiation-induced modification of polymer properties, and for selection of polymers for use in radiation environments. This means that the detailed chemical reactions resulting from absorption of radiation must be known. This fundamental understanding must enable us to relate the chemical structure of a polymer to changes in its chemical, physical and material properties. Such structure-property relationships require a great deal of research work, but they are the key to further advancement on a scientific basis. 

Polybrominated Biphenyls. In air, the two processes that may result in significant degradation or transformation of PBBs are photooxidation by hydroxyl radicals and direct photolysis. The estimated half-life of pentachlorobiphenyl in air due to reaction with hydroxyl radicals is 41.6 83.2 days (Atkinson 1987a). Based on a structure-activity relationship for the estimation of half-lives for the gas-phase reactions of hydroxyl radicals with organic compounds (Atkinson 1987b), the estimated half-lives of hexabromobiphenyl and decabromobiphenyl due to reaction with OH radicals are 182 and 2,448 days, respectively. These half-lives are consistent with the half-life of pentachlorobiphenyl due to reaction with OH radicals. However, the half-lives of brominated biphenyls expected to be present in the particulate phase in the air may be even longer than the estimated half-lives due to gas phase reaction. Therefore, the Iransfonnation of the hexa- and other higher brominated PBBs in the atmosphere due to reaction with OH radicals may not be irrportant. 

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