Polyalkenes oxidation

D. E. Graham, W. A. Lidy, P. C. McGrath, andD. G. Thompson. Demulsifying process using polysiloxane polyalkene oxide block copolymer. Patent AU 565533,1987. 

Jeffcoate CS, Gershun AV, Woyciesjes PM, Marinho FJ (2003) Heat transfer composition for fuel cell assembly, e.g. proton exchange membrane fuel cell, comprises alcohol, polyalkene oxide, additive, and water. United States Patent Number US 7,481,948 B2... 

Accelerators These increase the rate of polymerization. They should not be confused with polymerization initiators as they are not sufficiently nucleophilic to induce polymerization. The compounds described in the literature have one common feature, namely, they are all capable of sequestering alkali metal cations. The mechanism by which accelerators function is not clear, but it is believed to involve either increasing ion separation at the growing chain end or activation of anions on the substrate by cation sequestration to give so-called naked anions in the liquid adhesive. Examples of compounds used as accelerators are crown ethers (II), polyalkene oxide (III), podands (IV) and calixarenes (V). 

Studies on the mechanism of polyalkene oxidation have shown that hydroperoxides are its primary products, which then decompose to form other oxygen-containing compounds. The oxidation of polyalkenes is described by a radical-chain scheme as follows. Initiation may occur with the formation of radicals R or RO - ... 

A interesting and useful reaetion is the intramolecular polycyclization reaction of polyalkenes by tandem or domino insertions of alkenes to give polycyclic compounds[l 38]. In the tandem cyclization. an intermediate in many cases is a neopentylpalladium formed by the insertion of 1,1-disubstituted alkenes, which has no possibility of /3-elimination. The key step in the total synthesis of scopadulcic acid is the Pd-catalyzed construction of the tricyclic system 202 containing the bicyclo[3.2. Ijoctane substructure. The single tricyclic product 202 was obtained in 82% yield from 201 [20,164). The benzyl chloride 203 undergoes oxidative addition and alkene insertion. Formation of the spiro compound 204 by the intramolecular double insertion of alkenes is an exam-ple[165]. 

Table 8.12 shows a selection of elemental analyses of polymers after oxidative wet digestion. Crompton [31] has described the determination of 0.1 ppm of copper in polyalkenes by means of wet digestions of... 

Oxidation of polyalkenes is accompanied by the degradation of macromolecules [11,12,33-41,122,123]. Thus, when HDPE is oxidized in chlorobenzene to a concentration of hydroperoxyl groups of 0.12mol L 1 (378 K, 1 h) and 0.20mol L 1, the mean molecular weight of... 

As follows from the comparison of the rates of oxidation and destruction of linear and branched polyalkenes, the branched form possesses more susceptible tertiary C—H bonds and oxidizes more rapidly (but degrade more slowly) than the linear form. This was observed for PS, PE, PP, polyfrt-isopropyl styrene), polymethylene, and polymers produced by the decomposition of diazomethane-diazoethane and diazomethane-diazobutane mixtures [125], The number of cleavages per oxygen molecule consumed at 403 K amounts to 0.25 for PE and to 0.04 for PP. 

A combined addition of a chain-breaking inhibitor and a hydroperoxide-breaking substance is widely used to induce a more efficient inhibition of oxidative processes in polyalkenes, rubbers, lubricants, and other materials [3 8]. Kennerly and Patterson [12] were the first to study the combined action of a mixture, phenol (aromatic amine) + zinc dithiophosphate, on the oxidation of mineral oil. Various phenols and aromatic amines can well serve as peroxyl radical scavengers (see Chapter 15), while arylphosphites, thiopropionic ethers, dialkylthio-propionates, zinc and nickel thiophosphates, and other compounds are used to break down hydroperoxide (see Chapter 17). Efficient inhibitory blends are usually prepared empirically, by choosing such blend compositions that induce maximal inhibitory periods [13],... 

Pincer-ligated iridium complexes have been used as homogeneous catalysts for the dehydrogenation of aliphatic polyalkenes to give partially unsaturated polymers. The catalyst appears to be selective for dehydrogenation in branches as compared with the backbone of the polymer.56 The mechanism shown in Scheme 1 has been suggested for an [IrCl(cod)]2-catalysed oxidative esterification reaction of aliphatic aldehydes and olefinic alcohols.57... 

Polymers of thietanes have been converted to the corresponding polysulf-oxides and polysulfones. A blend of preformed polyalkene [e.g., polypropylene] and poly(thietane) has been milled and molded and is used for making fibers, films, bottles, and pipes. ... 

Bromohydration, Bromolactonization, and Other Additions to C=C. The preferred conditions for the bromohydration of afkenes involves the portionwise addition of solid or predissolved NBS (recrystallized) to a solution of the alkene in 50-75% aqueous DME, THF, or f-butanol at 0 °C. The formation of dibromide and a-bromo ketone byproducts can be minimized by using recrystallized NBS. High selectivity for Markovrukov addition and anti stereochemistry results from attack of the bromonium ion intermediate by water. Aqueous DMSO can also be used as the solvent however, since DMSO is readily oxidized under the reaction conditions, significant amounts of the dibromide byproduct may be produced. In the bromohydration of polyalkenic compounds, high selectivity is regularly achieved for attack of the most electron-rich double bond (eq 20). With famesol acetate, squalene, and other polyisoprenes, choice of the optimum proportion of water is used to effect the selective bromohydration at the terminal double bond (eq 21), and the two-step sequence shown is often the method of choice for the preparation of the corresponding epoxides. ... 

It is believed that copper or copper oxide is a catalyst for the oxidation of polyalkenes. For this reason, polymers to be used for coating copper wire should be run in copper or oxidized copper sample pans. Coating for aluminum wire should be run in aluminum pans. From an Arrhenius plot of the logarithm of oxidative induction time against reciprocal temperature, the oxidation energies were obtained as 110.9 kj mol" for an aluminum pan and 37.2 kJ mol" for a copper pan [4-6]. 

Figure 11.17. Examples of unsaturated fatty acids. Large numbers of such alkenes both as ( )- and (Z)-isomers exist. The intermediate in the oxidation of arachidonic acid to (only one shown member of the) prostaglandins is part of a cascade of reactions to an entire family of compounds that vary in oxidation state. Leukotrienes (three conjugated double bonds and no five-membered ring) and thromboxanes with six-membered oxygen-containing rings (oxa-cyclohexane, pyran, oxane) are also derived from C20 polyalkenes.

The difference between Method 1 for the determination of water and volatiles in polyalkenes and that described below for the determination of water and volatiles in vinyls and acrylics, is that in the latter method, the polymer is heated in the presence of the residual air in the sample tube, and in the first method (polyalkenes) the residual air in the sample tube is replaced with inert carrier gas, helium, before the sample is heated. With the non-olefinic polymers the same results for water content are obtained by both methods, ie. it is not necessary to replace the air with inert gas. Polyalkenes, however, are oxidized if heated in the presence of air, thus producing additional amounts of water. Jeffs recommends that before carrying out any quantitative work on the volatile constituents obtained from a polymer powder, a preliminary gas-chromatographic investigation should be carried out, of their complexity. For example, one polymer showed nine components other than air, water and the original monomer. These... 

The method is capable of determining down to 0.05% of diorganosulphide and tertiary phosphite type antioxidants in polyalkenes with an accuracy of 5%. Table 7.8 shows the results obtained by applying the oxidation method to blends of antioxidants in unstabilized polyethylene. The results are in excellent agreement with the theoretical antioxidant content of these polymers. 

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