Reactive mixing mechanical considerations

Considerations of mixed mechanisms and mixed reactive states might apply to these cases also, but there is no direct evidence that cyclo-hexenone itself reacts from other than the lowest zn-n state. Both cis and trans products are produced, except possibly in the acrylonitrile reaction 97>, and cis and trans-2-butene give the same mixture of products. A predominant biradical mechanism would seem the logical choice. 

Earlier studies of numerous research groups have considerably helped to establish a basic understanding of the mechanism of various types of micellar catalysis. Several excellent accounts of prior work have been published [4-8]. Pseudophase treatments of reactivity in association colloids provide a chemically satisfying approach with predictive power [9]. The present section of this article focuses on a few examples from recent literature that explore the catalytic effects observed from aqueous micellar or mixed-micellar aggregates. 

A catalyst. for the direct reaction is desirable, not only to improve the reactivity and yield, but also to smooth the reaction and make the result more reproducible than otherwise would be the case. One effective catalyst is metallic copper, which may be powdered and mixed with the silicon or (better still) sintered with the silicon by heating the mixture in hydrogen.16 The initial distribution of the catalyst has much to do with the behavior of the reaction during the early stages, as is evident upon consideration of the proposed mechanism for the reaction.17... 

In the manufacture of ferrites, the raw materials (usually oxides and carbonates) are wet mixed in ball mills. The raw materials should be suitably fine to be reactive and must not contain harmful impurities. The mix is then pre-reacted at temperatures lower than the actual firing temperature. This pretreatment provides conditions for the actual synthetic reactions whose mechanisms show considerable differences. The three following basic types can be distinguished. 

A few spontaneous copolymerizations between exceptionally reactive donor acceptor olefinic pairs have been observed. Miller and Gilbert [37] observed that vinylidene cyanide spontaneously copolymerized with vinyl ethers when the two monomers were mixed at room temperature. Yang and Gaoni [38] observed that 2,4,6-trinitrostyrene as the acceptor monomer spontaneously copolymerized with 4-vinylpyridine as the donor monomer when the two were mixed at room temperature. Butler and Sharpe [39] reported that divinyl ether and divinyl sulfone spontaneously copolymerized upon monomer mixing. Thus, the participation of the charge-transfer complex in the copolymerization mechanism of such strong electron donor electron acceptor monomer pairs appears to have considerable support. 

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