Fluoroethylenes, relative rates

Table 7 in Section 3, showed that the pre-exponential, 4-factor for the addition of alkyl radicals to olefins is of the order 10s 1 mol-1 s-1. Table 17 (p. 68) lists the relative Arrhenius parameters (taking ethylene as standard) for the addition of a wide range of halogenoalkyl radicals to fluoroethylenes. These tables correspond to the relative rate tables discussed in Section 5 in which the... 

In Table 5 (p. 55) we compared the relative rates of addition of methyl, fluoromethyl, difluoromethyl and trifluoromethyl radicals to ethylene and tetra-fluoroethylene. Figure 3 shows the Arrnehius plots for these competitive reactions. These indicate in a very graphic way the fact that this systematic variation in relative rate can be entirely attributed to variation in the activation energy differences. 

The general rule, therefore, is that radicals add to the less substituted end of C-, Z- or X-substituted alkenes to give the more stable radical, this usually matches the coefficients in the appropriate frontier orbitals, and the relative rates are usually, but not always, in line with the appropriate frontier orbital separations.994 This is true of fluoroethylene 7.42, which unexceptionably adds methyl and trifluoromethyl radicals predominantly at the less-substituted carbon. 

Tubular blood-contacting polymeric materials were modified by plasma polymerization and evaluated in animals (baboons) with respect to th r c iadty to induce acute and chronic arterial thrombosis. Nine plasma polymers based on tetrafluoro-ethylene, hexafluoroethane, hexafluwoethane/H, and methane, when deposited on silicone rubber, consumed platetets at rates ranging from l.l-5.6x 10 platelets/on day. Since these values are close to the lower detection limit for this test system, tl plasma polymers were considered relatively nonthrombogenk. Thus, artificial blood tube made of polyesters, having the inner side coated with plasma-pcrfymerized tetra-fluoroethylene, is now commercially available. 

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