Giese studies

No single factor can be identified as determining the outcome of radical addition. Nonetheless, there is a requirement for a set of simple guidelines to allow qualitative prediction. This need was recognized by Tedder and Walton,2 17 Beckwith ei ah, Giese. and, most recently, Fischer and Radom.4 With the current state of knowledge, any such rules must be partly empirical and, therefore, it is to be expected that they may have to be revised from time to time as more results become available and further theoretical studies are carried out. 1 lowever, this does not diminish their usefulness. 

Alkyl mercuric hydrides are generated in situ by reduction of an alkyl mercuric salt with sodium borohydridc (Scheme 3.91). Their use as radical traps was first reported by Hill and Whitesides491 and developed for the study of radical-olefin reactions by Giese,489490 Tirrell492 and coworkers. Careful choice of reagents and conditions provides excellent yields of adducts of nucleophilic radicals (e.g. -hexyl, cyclohexyl, /-butyl, alkoxyalkyl) to electron-deficient monomers (e.g. acrylics). 

Rare-Gas-Hydrogen Reactions. Ion-molecule reactions in the rare gas-hydrogen system are of great interest both theoretically and experimentally. The properties of the reactants and products are well known or may be calculated, and the properties of the intermediate three-body complex pose a tractable theoretical problem. Systematic studies of cross-section energy dependence and isotope effects in these systems have been undertaken by Friedman and co-workers (29, 47, 49, 67), by Koski and co-workers (2, 3), and by Giese and Maier (15, 16). 

In parallel with the development of the heterolysis of b-substituted alkyl radicals, a rearrangement reaction was observed and extensively studied in organic solvents. This rearrangement was first noted for b-(acyloxy)alkyl radicals (Scheme 5) by Surzur et al. [48] and, later, for b-(phosphatoxy)alkyl radicals by the Crich and Giese groups [49,50]. 

In a systematic study of the addition of cyclohexyl radicals to a-substi-tuted methyl acrylates, Giese (1983) has shown that the captodative-substituted example fits the linear correlation line of log with o-values as perfectly as the other cases studied. Thus, no special character of the captodative-substituted olefin is displayed. More recently, arylthiyl radicals have been added to disubstituted olefins in order to uncover a captodative effect in the rate data (Ito et aL, 1988). Even though a-A, A -dimethyl-aminoacrylonitrile reacts fastest in these additions, this observation cannot per se be interpreted as the manifestation of a captodative effect. Owing to the lack of rate data for the corresponding dicaptor- and didonor-substituted olefins, it is not possible to postulate a special captodative effect. The result confirms only that the A, A -dimethylamino-group, as expected from its a, -value, enhances the addition rate. In the sequence a-alkoxy-, a-chloro-, a-acetoxy- and a-methyl-substituted acrylonitriles, it reacts fastest. 

A number of investigators have studied the effect of ozone on the ultraviolet absorption spectra of proteins and amino acids. A decrease in the absorption of 280-nm light in a number of proteins was originally reported ly Giese et aV to be a consequence of ozone exposure they suggested that this was due to an interaction of ozone with the ring structures of tyrosine and tryptophan. Exposure of a solution of tryptophan to ozone resulted in a decrease in 280-nm absorption, whereas the extinction coefficient of tyrosine increased. Similar results with tyrosine were reported by Scheel et who also noted alterations in the ultraviolet spectra of egg albumen, perhaps representing denaturation by ozone. 

Less is known about the interaction of ozone with other macromolecules. Alterations of nucleic acids in solution have been reported by Qiristensen and Giese, and in Escherichia coli by Prat et in studies with relatively high concentrations of ozone. Both purines and pyrimidines are attacked by ozone. However, the detailed chemistry of the reaction, including the intermediates and end products, has not been fiilly elucidated. This may be important, in view of the chromosomal effects of ozone, although such effects are most likely due to the interaction of an ozone-induced intermediate with DNA, rather than to ozone itself. 

Freeze RA, Cherry JA (1979) Groundwater. Prentice-HaU Englewood Cliffs, NJ Gapon EN (1933) Theory of exchange adsorption in soils. J Gen Chim 3 144-163 Giese RF, Jr. (1982) Theoretical studies of the kaolin minerals Electrostatic calculations. Bull Mineral 105 417 24. 

Zerull, R., and R. H. Giese, 1974. Microwave analogue studies, in Planets, Stars and Nebulae Studied with Photopolarimetry, T. Gehrels (Ed.), University of Arizona Press, Tucson, Ariz., pp. 901-915. 

Clay Minerals and Clay Colloids. The literature on clays and clay colloids is expansive, but there remains a degree of uncertainty in many areas of their study due to their inherent heterogeneity. Descriptions of the structures and properties of clay minerals can be found in Grim (1968), Brindley and Brown (1980), Newman and Brown (1987), Sposito et al. (1999), and Giese and van Oss (2002). 

Giese et al. [25] have compared the steric course of the reaction ofTj (triplet) and S, (singlet) by studying the photocydization reaction of alanine derivatives 69, which led to the formation of proline derivatives 71a and 71b (Table 8.3)... 

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