Oxidative degradation of olefins

To remove halogen-containing side chains by means of nitric acid it is necessary to add silver nitrate, which binds the halogen that causes the difficulty. 

Chromic acid and potassium permanganate are more powerful oxidizing agents than nitric acid they usually convert all side chains into carboxyl groups. Like benzene homologs, alkylpyridines can also be oxidized, yielding pyridinecarboxylic acids, e.g., isonicotinic acid from 4-ethylpyridine  

4-Ethylpyridine (160 g) and water (300 ml) are warmed to 80° then a solution of potassium permanganate, (960 g) in water (41), prewarmed to 80°, is added at such a rate that the mixture boils continuously. Then the whole is boiled for a further 15 min after which the manganese oxides are filtered from the hot mixture. These oxides are well washed with water, and the filtrate is evaporated (to 1 1) in a vacuum. The solution of potassium isonicotinate obtained is acidified at 60° to pH 3-4 by concentrated hydrochloric acid and then cooled to 20°. Isonicotinic acid (165 g, 90%) separates and is collected. 

Degradation of phenol homologs to phenolic carboxylic acids by an oxidative 

The oxidants named above degrade phenol homologs to phenolic carboxylic acids only if the hydroxy group is protected, e.g., as alkoxy group. However, the free phenolic carboxylic acids can be obtained directly from phenol homologs if the side chains are oxidized away by air in an alkali melt e.g., in an alkali melt thymol affords 2-hydroxy-4-methylbenzoic acid, among other products.105 

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CL must be very carefully purified to exclude small concentrations of (1) ferric ions which would catalyze die thermal oxidative degradation of polycaprolactam and (2) aldehydes and ketones which would markedly increase oxidizability of CL. The impurities in CL may retard die rate of CL polymerization as well as having a harmful effect on die properties of die polymer fiber. In die vacuum depolymerization of nylon-6, a catalyst must be used because in die absence of a catalyst by-products such as cyclic olefins and nitrides may form, which affects the quality of die CL obtained.1... 

Oxidative damage, role of ascorbic acid in preventing, 25 769 Oxidative degradation, 70 682 of gasoline, 72 399-400 Oxidative dehydrogenation, 23 342-343 Oxidative pyrolysis, 27 466 Oxidative stability, of olefin fibers, 77 229 Oxidative stability test, 72 400 Oxide crystal glass-ceramics, 72 641 Oxide-dispersion-strengthened alloys, 77 103-104... 

Oxidizing splitting of olefinic side chains forms dione 22 from benzal 21 (62CPB366) and aldehyde 10a from quaternized and Hofmann-degraded... 

Moreover, XPS data also indicate that this Os reduction may be accompanied by oxidative degradation of the polymer. Not only the Os speciation but also the oxidant preference seem different for Herrmann s Os/PVP catalyst. Only H2O2 was an effective oxidant even in this case, extreme oxidant excesses were applied to convert the olefins ... 

We report here the hydrogenation of cycloalkenes using Rh-supported montmorillonite as a catalyst. The catalyst preparation was based on oxidative degradation of intercalated tris-(phenanthroline)-Rh(III) followed by reduction under hydrogen atmosphere. There is no obvious trend observed in the hydrogenation yields of the olefins. The most notable difference in the hydrogenation behaviour is seen in case of cyclopentene/cyclooctene both olefins could be efficiently hydrogenated in their pure form but there was no conversion of cyclooctene in presence of cyclopentene. 

In conclusion, singlet oxygen plays a role in the photo-oxidative degradation of polymers containing olefinic unsaturations. Polymers that do not contain these groups, e.g. poly(vinyl chloride), poly(methyl methacrylate), polystyrene, etc., are unreactive [24]. 

The more serious cause of deterioration in rubbers is its reaction with atmospheric oxygen. This is possible because rubber is a diene polymer and some, such as natural rubber, EPDM, SBR, nitrile rubber, and butyl rubber, have olefinic double bonds in their structure. Much research work is being done on the oxidative degradation of unvulcanized rubbers, but this is not relevant to the resistance of vulcanized rubbers in storage or in service as their aging behaviors differ widely. Unvulcanized rubber compound has to be vulcanized in order to produce usable products. The nature of the cross-link produced varies considerably, and this can affect the balance of chemical and particularly of physical properties of the vulcanizates. 

Over the last few years a number of applications on the analysis of olefin copolymers have been published that make use of the LC-Transform system. These include the SEC-FTIR analysis of ethylene/vinyl acetate copolymers [117], ethylene/ methyl methacrylate copolymers [118, 119], ethylene/styrene copolymers [120], HOPE and PP [121]. A number of studies used SEC-FTIR for monitoring the thermo-oxidative degradation of polyolefins [122-126] and a combination of TREE and SEC-FTIR to investigate the complex structure of olefin copolymers [127,128]. 

The photodegradation and photo-oxidative degradation of different poly-olefins have been subjects of many publications (Table 3.1) and reviews [570, 853, 856, 866, 1999, 2268]. 

Polyisobutylene has the chemical properties of a saturated hydrocarbon. The unsaturated end groups undergo reactions typical of a hindered olefin and are used, particularly in the case of low mol wt materials, as a route to modification eg, the introduction of amine groups to produce dispersants for lubricating oils. The in-chain unsaturation in butyl mbber is attacked by atmospheric ozone, and unless protected can lead to cracking of strained vulcanizates. Oxidative degradation, which leads to chain cleavage, is slow, and the polymers are protected by antioxidants (75). 

On the other hand, the storage stability of biodiesel is adversely affected by the presence of unsaturated alkyl components. The olefinic moieties in biodiesel fuel can undergo oxidative degradation via exposure to air with deleterious results, including formation of solids and gums. The degree of oxidative degradation has been shown to increase with fuel unsaturation. 

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