Activity unifying role

This review illustrates the above delineated characteristics of electron-transfer activated reactions by analyzing some representative thermal and photoinduced organometallic reactions. Kinetic studies of thermal reactions, time-resolved spectroscopic studies of photoinduced reactions, and free-energy correlations are presented to underscore the unifying role of ion-radical intermediates [29] in—at first glance—unrelated reactions such as additions, insertions, eliminations, redox reactions, etc. (Photoinduced electron-transfer reactions of metal porphyrin and polypyridine complexes are not included here since they are reviewed separately in Chapters 2.2.16 and 2.2.17, respectively.)... 

In contrast, it is a central thesis of this book that the disciplinary boundary between physics and chemistry became less well defined after 1900 than in the middle decades of the nineteenth century and that physical chemistry played an important role in this development. It is equally a central thesis of this study that a compelling and unifying interest among organic, inorganic, and physical chemists, that is, of chemists, was the problem of chemical affinity and the dynamics of chemical activation and reaction. 

The remaining two reviews treat active topics in applied chemical kinetics. Wehner provides a unified treatment of the theory of flames, including the role of intermediates and the problems of flammability limits and ignition conditions. Sinfelt discusses the near-simultaneous conduct of successive reactions needed, for instance, in the reforming of petroleum fractions, as produced by intimate mixtures of metallic and acidic catalysts. 

The four chapters within the Chemistry section discuss the effects of UVR on biogeochemical cycles of various elements (Chapter 5), the photochemistry of DOM (Chapter 6), the photo-activated toxicity of several natural and anthropogenic substances (Chapter 7) and the environmental implications of photoinduced formation of reactive oxygen species (Chapter 8). Once again, the central role of DOM emerges as a unifying theme. 

This paper will concentrate on three areas of photolysis where important questions concerning biological systems are addressed. The first will be the well-established but still vital area of the heme proteins that have photolabile ligands. The second area will be with the use of triplet probes on proteins and DNA. The third area covered will be those special proteins that are photochemically active. To avoid making technology take precedence over science, many experimental details will be discussed in the process of our attempt to provide a unifying thread to recent trends in biochemical photolysis. The authors will not attempt to discuss the various aspects of bimolecular kinetics. We will instead stress the aspects of photolysis where the protein is believed to play an important role in the overall kinetic picture. 

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