LO’radicals

The cycle accounts for 20—25% of the halogen-controUed loss (M is a third body molecule). The possible contribution of naturaUy occurring iodine compounds to ozone destmction (via I and lO radicals) is being investigated (79). 

Figure 18.2. Cholesterol autoxidation initiated by peroxy (LOO ) or alkoxyl (LO ) radicals arising from peroxidation of polyunsaturated fatty acids (LH). Compounds are as follows (1) CHOL (2) 7-CHOL (3) CHOO (4) 7a-OOH (5) 7fLOOH (6) CHO (7) 7a-OH (8) 7(3-OH (9) 7-keto (10) 7-keto-3,5-dien. For abbreviations, see Table 18.1.

Propagation by Alkoxyl Radicals, LO Alkoxyl (LO ) radicals are responsible for propagation of the radical chain during the very rapid oxidation that ensues after the induction period ends. In the earliest stages of oxidation, LOO cyclization and addition reactions can proceed before LOOH formation via H abstraction, but LO can only be generated via LOOH decomposition, so their reactions become important as secondary events in oxidation. Nevertheless, because LO react faster than LOO by several orders of magnitude, LO becomes dominant almost as soon as LOOH breaks down. 

Iron ions cleave LOOHs in a Fenton like reaction to LO radicals (Scheme 14). 

Scheme 14 Generation of LO radicals by a Fenton like reaction.

The reaction constant, k = 9 x 10 cm molec" s . At the average global concentration of OH (about 8 X lO radicals this reaction alone would be responsible... 

Nitric oxide can act as a vitamin E-like inhibitor of radical chain propagation reactions via radical-radical reaction with cytotoxic species such as lipid peroxyi (LOO-) and aikoxyl (LO-) radicals. Nitric oxide reacts with yLO- and LOO- at near-diffusion-limited rates (for LOO-, ife = 1.3 X 10 M sec" ) (Padmaja and Huie, 1993). This rate constant... 

Quantitatively compare the rate and degree of polymerization of styrene polymerized in bulk at 60 C with an emulsion polymerization (case 2 behavior h = 0.5) containing 1.0 X 10 polymer particles per milliliter. Assume that [M] = 5.0 molar, /f,- = 5.0 x lO radicals per milliliter per second, and all rate constants are the same for both systems. For each polymerization system, indicate the various ways (if any) by which the polymerization rate can be affected without affecting the degree of polymerization. 

Oxygen plasma was generated in a GSC-200 plasma genmator. The concentration in oitygen plasma was around lO" radicals (or ions) per liter. Oxygen plasma erosion rates were determined by measuring weight loss after treatment The effect of tiie addition of clay on tiie solvent iq>take properties of Epon 862/W was examined. Seven Epon 862/W panels were made with 0%... 

Hypochlorous acid HOCl, hypobromous acid HOBr, and hypoiodous acid HOI are formed in the chain termination reactirais between CIO, BrO, lO radicals and HO2 radicals. Since they have absorption spectra in the ultraviolet to visible regirai, the photolytic regeneration of the radicals has to be considered in the atmosphere. 

The gaseous CIO, BrO and lO radicals have all been observed by uv absorption spectroscopy in both static and flow systems. However, no optical or epr spectrum of the gaseous FO radical has... 

Take kp for styrene as 500L/molsec and [M] as 5.2mol/L at 50°C. Let there be lO particles/em of water. Let primary radicals be generated in water at the rate of lO radicals/sec (cm of water) (= p). Calculate r. Calculate p using the following relation ... 

---