Oxygenate initiation

Solution polymerization of VDE in fluorinated and fluorochlorinated hydrocarbons such as CEC-113 and initiated with organic peroxides (99), especially bis(perfluoropropionyl) peroxide (100), has been claimed. Radiation-induced polymerization of VDE has also been investigated (101,102). Alkylboron compounds activated by oxygen initiate VDE polymerization in water or organic solvents (103,104). Microwave-stimulated, low pressure plasma polymerization of VDE gives polymer film that is <10 pm thick (105). Highly regular PVDE polymer with minimized defect stmcture was synthesized and claimed (106). Perdeuterated PVDE has also been prepared and described (107). 

Electronic excitation from atom-transfer reactions appears to be relatively uncommon, with most such reactions producing chemiluminescence from vibrationaHy excited ground states (188—191). Examples include reactions of oxygen atoms with carbon disulfide (190), acetylene (191), or methylene (190), all of which produce emission from vibrationaHy excited carbon monoxide. When such reactions are carried out at very low pressure (13 mPa (lO " torr)), energy transfer is diminished, as with molecular beam experiments, so that the distribution of vibrational and rotational energies in the products can be discerned (189). Laser emission at 5 p.m has been obtained from the reaction of methylene and oxygen initiated by flash photolysis of a mixture of SO2, 2 2 6 (1 )-... 

Substituted nonheat-reactive resins do not form a film and are not reactive by themselves, but are exceUent modifier resins for oleoresinous varnishes and alkyds. Thein high glass-transition temperature and molecular weight provide initial hardness and reduce tack oxygen-initiated cross-linking reactions take place with the unsaturated oils. 

The determination of organic compounds by their direct catalytic effect on indicator reaction rates is a relatively unexplored ai ea promising valuable analytical chai acteristics, as we have recently shown in the determination of traces of unsymmetrical dimethylhydrazine (UDMH) by the oxidation of 3,3, 5,5 -tetramethylbenzidine (TMB) by atmospheric oxygen initiated with persulfate [1]. 

It is therefore not surprising to find that where boiler systems operate under these constraints, they suffer rapid and extensive oxygen-initiated corrosion to the internal surfaces of the FW system, the feed lines, the boiler shell, and all internal heating surfaces. With poor oxygen scavenging, heavy pitting corrosion and tuberculation is found, especially on the tubes and at the waterline of the FW tank and boiler shell. 

Each part of dissolved oxygen initially present in the wastewater produces 6.1 parts of sulfuric acid. 

Scheme 4.34. Singlet oxygen-initiated transformation of furan 4-158 into I itseaverticil lo I B...

Unlike a geometrical factor, the value of the factor

with composition in a predictable way. To illustrate this, suppose that stoichiometric MO2 is heated in a vacuum so that it loses oxygen. Initially, all cations are in the M4+ state, and we expect the material to be an insulator. Removal of O2- to the gas phase as oxygen causes electrons to be left in the crystal, which will be localized on cation sites to produce some M3+ cations. The oxide now has a few M3+ cations in the M4+ matrix, and thermal energy should allow electrons to hop from M3+ to M4+. Thus, the oxide should be an n-type semiconductor. The conductivity increases until

reduction continues, eventually almost all the ions will be in the M3+ state and only a few M4+ cations will remain. In this condition it is convenient to imagine holes hopping from site to site and the material will be a p-typc semiconductor. Eventually at x = 1.5, all cations will be in the M3+ state and M2C>3 is an insulator (Fig. 7.3). 

For the oxygen-initiated polymerisation, nearly 1500 atmosphere pressure and 200°C is used having 0.05-0.1 percentage oxygen. The reaction is highly exothermic and efficient heat dissipation becomes essential. The reaction temperature is above the critical temperature of ethylene so that the ethylene is in the gas phase. 

Also autooxidation or auto-oxidation. A slow, easily initiated, self-catalyzed reaction, generally by a free-radical mechanism, between a substance and atmospheric oxygen. Initiators of autoxidation include heat, light, catalysts such as metals, and free-radical generators. Davies (1961) defines autoxidation as interaction of a substance with molecular oxygen below 120°C without flame. Possible consequences of autoxidation include pressure buildup by gas evolution, autoignition by heat generation with inadequate heat dissipation, and the formation of peroxides. 

Acetylation occurs at the 2-position of allene systems (Scheme 8.14). The intermediate 7t-allyl complex breaks down via the nucleophilic displacement of the cobalt carbonyl group by the hydroxide ion to produce the hydroxyketone (7) [ 11 ]. An alternative oxygen-initiated radical decomposition of the complex cannot, however, be totally precluded. The formation of a second major product, the divinyl ketone (8), probably arises from direct interaction of the dicobalt octacarbonyl with the allene and does not require the basic conditions. 

The total synthesis of litseaverticillols D, F and G (172 and 173), which are natural products with anti-HIV activity, was achieved recently via a singlet oxygen initiated cascade proposed to be biomimetic (Scheme 64). Finally, allylic alcohols 174a and 174b (Scheme 64) were isolated in a 4/1 ratio via a stereoselective singlet oxygen ene reaction. Stereoisomer 174a is an intermediate in the synthetic route of staurosporine, which is a bioactive alkaloid with hypotensive, antimicrobial and cell cytotoxic properties. 

Corrosion inhibitor Two inhibitors could be used a. Copper corrosion inhibitor to help prevent sulfur, hydrogen sulfide, and mercaptan attack on copper b. Ferrous metal corrosion inhibitor to prevent water/oxygen initiated corrosion of iron and steel system components... 

An X-ray crystal structure of 55, redrawn as Fig. 10, supported the formulation of the complex as that of a peroxo system. Further, the structure demonstrated that no interactions between the [Of-] ligand and the borate moiety were possible because of the relative arrangement of the [Of-] and borate ligands about the iridium center. Such interactions were implicated in the oxygen-initiated decomposition of the iridium complex of 52, while the lack of reactivity of the iridium complexes of 53 and 54 was attributed to steric factors arising from the alkyl chains connecting the sulfur atoms. 

It is well known that runaway of LDPE reactors occurs when the concentration of peroxide or oxygen initiator is too high, because of malfunction of the initiator-metering device. It can... 

Mixing the two organics on millimolar scale under an oxygen atmosphere caused an explosion. The experimenters believe that addition of the silane to the triple bond is oxygen initiated. The propynoate will surely have been within flammable limits in the headspace, even if the silane were not. 

Hanst and Calvert64 photooxidized azomethane at room temperature proceeding to about 50% decomposition. They put forward the idea that ozone was an intermediate in the oxidation and showed that it was removed rapidly only when photolysis was taking place. However, this merely proves that ozone will react with one of the radicals produced in the system. Similarly, the test which they used for ozone (tetramethyl-ethylene) was not shown to be specific to ozone and, indeed, is not likely to be. They were unable to detect methyl hydroperoxide in these experiments under conditions in which it was shown to be peculiarly stable at 200°C. for several hours. Formic acid was shown to be the major product of the prolonged further oxidation of formaldehyde in the presence of 1 atm. of oxygen (initially). 

Matsushita, S., Terao, J. 1980. Singlet oxygen-initiated photooxidation of unsaturated fatty acids and esters and inhibitory effect of tocopherols and (3-carotene. In Auto-oxidation in Food and Biological Systems (M.G. Simic, M. Karel, eds.), pp. 27 44, Plenum Press, New York. 

Terao, J., Yamauchi, R., Murakauri, H., Matsushita, S. 1980. Inhibitory effects of tocopherols and (3-carotene on singlet oxygen-initiated photooxidation of methyl linoleate and soybean oil. J. Food Proc. Preserv. 4, 79-93. 

---