Reactivity weak oxidizing agents

In contrast to the catalysts containing Ti that produce polymers with a broad MW distribution of 5 to 30, the compounds containing V produce polyethylene with a narrow MW distribution of 2-4. The V systems are suited to polymerization of higher a-olefins and for copolymerization. Therefore, these systems are used technically to make a rubber (EPDM type) by copolymerization of C2H4, propylene, and as diene ethylidene norbor-nene (ENB). These catalysts are initially very active because of the presence of V(III), which seems to be the active oxidation form. However, some of them lose activity by reduction after a short polymerization time. They can be reactivated by weak oxidizing agents (activator) like chlorobenzene. 

Fluorine is the most reactive of all elements, in part because of the weakness of the F—F bond (B.E. F—F = 153 kj/mol), but mostly because it is such a powerful oxidizing agent (E ed = +2.889 V). Fluorine combines with every element in the periodic table except He and Ne. With a few metals, it forms a surface film of metal fluoride, which adheres tightly enough to prevent further reaction. This is the case with nickel, where the product is NiF2. Fluorine gas is ordinarily stored in containers made of a nickel alloy, such as stainless steel (Fe, Cr, Ni) or Monel (Ni, Cu). Fluorine also reacts with many compounds including water, which is oxidized to a mixture of 02> 03> H202, and OF2. 

The double bond in an oxygen molecule, depicted 6 = O , is strong enough to keep 0 from being too reactive, hence unable to accumulate in the atmosphere, but weak enough to allow Oj to be the oxidizing agent in combustion processes. 

For the 1,3-dithiane-1-oxide (R=H) case molecular dynamics simulations at the experimental temperature revealed that the R-hydroxysulfoniiun cation was considerably more stable than the more weakly adsorbed 1,3-dithiane molecule We consider that the hydroxydithiane cation may act as a proton transfer agent and this may account for the enhanced reactivity of this system. 

---