Conjugation sacrificial

Electrochemical cyclopropanation of alkenes occurs using dibromomethanes at a sacrificial zinc electrode in a CH2C12/DMF mixture with a one compartment cell (equation 65). Yields using more than twenty isolated and conjugated olefins were generally good (30 to 70%)98. Benzal halides give only poor yields in the same reaction, but 2,2-dibromo-propane leads to the equivalent gem-dimethylcyclopropanes in fair yields. The method represents a useful alternative to other methods of cyclopropanation of olefins such as the Simmons-Smith reaction. 

The very reactive radicals R are blocked by being transformed into a neutral molecule (RH) and a radical of very low reactivity stabilised by conjugation. In that way the chain reactions are interrupted. Both antioxidants (hindered phenols and diphenylamines) are consumed after hydrogen radical donation (sacrificial antioxidants) [140]. 

Figure 3.11 Comparison of contributing resonance structures in sacrificial and isovalent conjugation and...

Figure 3.12 Contrasting energy costs for the rotation around the central C-C bond in 1,3-butadiene and 1,3-butadienyl radical cation illustrates the differences between sacrificial and isovalent conjugation.

Adsorbed antigen Gelatin Antibody-glucose oxidase (sacrificial antibody) conjugate... 

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