Cage reaction definition

Finally the most definitive evidence for a cage reaction was the observation that when an equimolar mixture of the peroxide (48) and the peroxide-dio (48-Djo) were decomposed, no crossover products were obtained only equal amounts of fully protonated hydrocarbon (49) and the hydrocarbon-d (49-0 ) were formed. The optical purity of the isolated ( + )-(5)-1-methyl-2,2-diphenylcyclopropane (49) was found to be 31-37 % with a net retention of configuration. Thus, when the lifetime of the rapidly inverting g radical is sufficiently great to permit diffusion out of the solvent cage the product formed by the... 

Control of the particle size while retaining precise control over the release rate is enabled by compartmentalization of the sol-gel solution into droplets of definite size. This can be achieved by emulsification of the sol-gel solution by mixing it with a solution composed of a surfactant and a non-polar solvent (Figure 2.13). When an active molecule is located in the aqueous droplet of a W/O emulsion, encapsulation occurs as the silicon precursors polymerize to build an oxide cage around the active species. By changing the solvent-surfactant combination, the particle size can be varied from 10 nm to 100 pm as the size of the particles is controlled by the size of the emulsion droplet, which acts as a nano-reactor for the sol-gel reaction (Figure 2.13). 

A kinetic scheme is most easily worked out for the pure polymerization.106 It is useful first to make certain simplifying approximations and definitions. We replace Scheme 6 by Scheme 8, where In is an initiator producing radicals R , M is the monomer, Mn is the growing polymer chain, and M —Mm is combination product and Mn( H) are disproportionation products. If all radicals R produced by the initiator were available to start chains, we could write, from the first two reactions, kinetic Equation 9.40 for rate of change of R-concentration. Because of cage recombination, only some fraction f of the... 

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