Addition reactions experimental background

In the triple layer model one of the o-plane metal surface complexes is represented as bidentate, Eq. (6.9), while one of the P-plane metal surface complexes is represented as a hydroxy-metal surface species, Eq. (6.30). Davis and Leckie (1978) considered the hydroxy-metal complexation reaction to be more consistent with their experimental data. Often, an additional metal surface complex containing the background electrolyte anion is postulated to form in the P-plane ... 

If more DTNB is used, the excess aromatic thiol or disulfide could compete with the protein for Hg(II) and thus expose additional protein thiols for reaction with the DTNB reagent. Protein thiol titrations with DTNB are often subject to inaccuracies resulting from oxidation of the thiol residues, background DTNB hydrolysis, and the inherent uncertainty in measuring protein concentrations (161). Any or all of these factors may play a role in the discrepancies in results described above. In efforts to eliminate these contributions, we performed DTNB measurements with relatively low DTNB concentrations of O.OOlAf and at relatively low pH to eliminate hydrolysis interference. Protein concentration determinations were based on the experimentally determined extinction coefficient of 58(X) M cm found for MerR (145). 

This chapter focused upon reactions at unsaturated centers alkenes, alkynes, arenes, and carbonyls. A large variety of additions and eliminations was examined. The complexity in the examples showed how diverse the possibilities are for additions and eliminations to such centers. One can have electrophilic, nucleophilic, and radical pathways for almost all reaction classes, and the dominant product depends upon the structures of the reactants and the experimental conditions. You should now be able to write the electron pushing for the standard reaction mechanisms (El, E2, SeAr, etc.), as well as be able to predict and examine experimentally the variations that are possible. Given this background on unsaturated centers, we turn our attention to reactions that occur at saturated centers, which is the first major topic of the next chapter. 

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