Numerical solution scission

The fraction of monomer in the volatile species should be a strong function of the relative random scission rate and this is often taken as an indicator of the balance between end-chain and random scission in experimental observations.1 We should expect that when end-chain scission dominates, the fraction of monomer in the volatile species should be close to 1. As more random scissions occur, the fraction will reduce. When random scission dominates, the spectrum of volatile species should be approximately flat, implying that the fraction of monomers should approach I /(mv - 1) as a(r) —> °°. Figure 18.15 shows the monomer fractions (from numerical solutions of the... 

The stability of iron-peroxo complexes is marginal in heme systems in the presence of a strong proximal ligand (His, Cys, or Tyr), and the aqueous solution at a near-neutral pH. The numerous attempts to isolate such complexes obtained in reactions of hydrogen peroxide with P450 at ambient conditions have failed because of the inherent low stability and fast conversion to ferryl-oxo species with 0-0 bond scission There have been successful isolations of the ferriheme-peroxide complex in myoglobin, however . ... 

Polyisobutene is non-crystalline when unstretched and is therefore soluble at room temperature in hydrocarbons and halogenated hydrocarbons. The material is resistant to most acids, alkalis and aqueous solutions, as would be expected from its saturated hydrocarbon structure and absence of tertiary hydrogen atoms. The lack of tertiary hydrogen atoms renders polyisobutene more resistant to oxidation than polypropylene also, the less numerous and partially shielded methylene groups in polyisobutene are less reactive than those in polyethylene. However, polyisobutene is rather susceptible to thermal degradation since chain scission is favoured by the greater stability of the resultant tertiary free radical ... 

---