Concrete acid reactions

This study suggests a radically new explanation for the nature of Lewis acid activation in the Simmons-Smith cyclopropanation. The five-centered migration of the halide ion from the chloromethylzinc group to zinc chloride as shown in TS2 and TS4 has never been considered in the discussion of a mechanism for this reaction. It remains to be seen if some experimental support can be found for this unconventional hypothesis. The small energy differences between all these competing transition states demand caution in declaring any concrete conclusions. 

The initiation of the cationic polymerization of vinyl monomers by a Lewis acid MtXn in the absence or presence of a coinitiator can proceed in a number of ways depending on the concrete reaction conditions 1,2). 

The sulfuric acid that is generated on the moist sewer surfaces may react with the alkaline cement in the concrete. A simple stoichiometry of this reaction is given by the following expression ... 

Equations (6.10) and (6.11) imply that 32 g H2S-S through the formation of sulfuric acid has a potential for the reaction with 100 g of CaC03 of the cement in the concrete. The corrosion rate of the concrete can be expressed as follows (USEPA, 1974) ... 

In Section 3 it was shown that for those olefin polymerisations in solvents of DC about 10 which are ionic, propagation must be predominantly by free ions, under the usual polymerisation conditions. For the polymerisations by perchloric acid we can take a concrete numerical example by which it can be shown that ion-pairs (VI) cannot play any important part in the reaction. The relevant dissociation equilibrium is... 

Ceramicrete is an ex situ stabilization technology that uses chemically bonded phosphate ceramics to stabilize low-level radioactive waste and hazardous waste containing radionuclides and heavy metals. The technology mixes phosphates with acidic solution, causing an exothermic reaction similar to that used in forming concrete. But while concrete is based on relatively weak hydrogen and van der Waals bonding, Ceramicrete uses a combination of ionic, covalenf and van der Waals bonds to stabilize contaminants. 

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