Double bonds peroxide value

It is seen that the values of kd are very close. Hence, the reaction of POOH with the C—H bond is not the main initiation reaction. If the breakdown is a monomolecular process, the rate of O—O bond homolysis in polymer must be close to that in the gas phase. 2,2-Dimethylethyl hydroperoxide breaks down in the gas phase with a rate constant of 1.6 x 1013 exp(— 158/i 7) = 5.3 x 10 x s 1 (398 K, [4]), that is, by four orders of magnitude more slowly than in polymer. Hence, the decomposition reactions in the polymers are much faster than the monomolecular homolysis of peroxide. Decomposition reactions may be of three types (see Chapter 4), such as the reaction of POOH with a double bond... 

Apart from specifications as to origin, e.g. palm kernel oil, fats are normally supplied on the basis of established parameters. One of these is the iodine value. This reflects the tendency of iodine to react with double bonds. Thus, the higher the iodine value the more saturated the fat is. An iodine value of 86 would approximate to one double bond per chain, while an iodine value of 172 approximates to two double bonds per chain. Another parameter is the peroxide value. This attempts to measure the susceptibility of the fat or oil to free radical oxidation. The test is applied on a freshly produced oil and measures the hydroperoxides present. These hydroperoxides are the first stage of the oxidation process. Obviously, this test would not give reliable results if applied on a stale sample. 

Oxidation indices, 656-72 peroxide determination, 762-3 peroxide value, 656, 657-64 colorimetry, 658-61 definition, 657 direct titration, 657 electrochemical methods, 663-4 IR spectrophotometry, 661-3 NIR spectrophotometry, 663 UV-visible spectrophotometry, 658-61 secondary oxidation products, 656, 665-72 tests for stability on storage, 664-5, 672 thermal analysis, 672 Oxidative amperometiy, hydroperoxide determination, 686 Oxidative cleavage alkenes, 1094-5 double bonds, 525-7 Oxidative couphng, hydrogen peroxide determination, 630, 635 Oxidative damage... 

Very poor biodiesel and biodiesel blends do not shed water as effectively as conventional diesel fuel fuel haze, gelling, and low-temperature handling problems can develop if biodiesel is contaminated with water in storage and transport. Poor double bonds present in the methyl ester compounds are active sites for oxidation and condensation reactions peroxide values can increase fuel darkening and deposit formation in storage systems can occur the addition of oxidation inhibitors to biodiesel helps improve storage stability. 

The direct use of hydrogen peroxide has rarely been shown to be of practical value in the cleavage of double bonds. However, olefins which are activated towards nucleophilic attack are sometimes cleaved by excess alkaline hydrogen peroxide. For example, a-keto olefins can be cleaved to the aldehydes144 and cinnamaldehyde is cleaved via the epoxide to benzaldehyde (Figure 3.30).145... 

The synthetic value of the reaction lies in the modification of these organoboranes. The commonest reaction involves the decomposition of the borane by alkaline hydrogen peroxide. The highly nucleophilic hydroperoxide anion attacks the electron-deficient boron with the formation of an ate complex. Rearrangement of this leads to the formation of a borate ester which then undergoes hydrolysis to an alcohol in which an oxygen atom has replaced the boron (Scheme 3.15). The overall outcome of this reaction is the anti-Markownikoff hydration of the double bond. The regiochemistry is the reverse of the acid-catalysed hydration of an alkene. The overall addition of water takes place in a cis manner on the less-hindered face of the double bond. 

LOO additions increase with heat (289), extent of oxidation (290), and solvent polarity (266). Dimer levels of methyl linolenate autoxidized neat at room temperature varied from 0.1% to 10.1%, proportional to peroxide values (290). MLn autoxidized at 40°C to PV 1062 gave 6.8% dimers 80% of these were from LOO and 20% were from epidioxide-OO additions. The dimer linkages were mostly C—O—O—C at lower temperatures, but shifted to C—C and C—O—C as the temperature increased (276). At PV = 4002, LOO additions increased to 55% of the products. Epidioxide peroxyl radicals, in particular, showed a very strong tendency to add to double bonds, with greater than 90% dimerization at 40°C. 

Liquid polybutadienes without functional groups may be vulcanized on double bonds of the diene part of the polymeric chain in the presence of a sulfur-accelerating, redox, or peroxide system. However, only the sulfur-accelerating system is able to provide the maximal durability values. Sulfur also has other advantages such as low price, availability, and so on. The amount of involved sulfur in the system depends on the desired properties of the product. For hard RubCon, this is 47-55 mass parts per 100 mass parts of rubber. 

Radical cyclization. Amido radicals are generated from A -methyldithiocarbonyl-hydrazides by heating with dilauroyl peroxide. Setting up the functional group in juxtaposition to a double bond invites intramolecular addition that even further implications in ring formation are envisaged. As a key step in a synthesis of the amaryllidaceae alkaloid fortucine the value of such a process is demonstrated. ... 

Table II shows that as the number of conjugated double bond increased from 10 to 11, the API of soybean oil increased at the concentrations of 100 and 200 ppm carotenoids. It has been reported that as the number of conjugated double bonds of carotenoids increased, the peroxide values of chlorophyll-sensitized photooxidation of soybean oil decreased significantly 16,17). Therefore, the singlet oxygen quenching ability of carotenoids was dependent on the number of conjugated double bonds of the carotenoids as reported by Lee and Min 16), Jung and Min 17), and Hirayama el al. (23).

Conjugated dienes and trienes measure the shift of double bonds. The shift is measured by the absorbences at 232 and 268 nm. Similar to the peroxide value, the absorbance at 232 nm measures the level of reactive intermediates. values, which are very low in unheated oils, may become as high as 15 within a few days of commercial frying. values at 268 nm follow changes in the iodine value, viscosity, PEFA, and polymer content. 

O/CD/0 entropy value of (CH3)2C=CHOOH which contains two methyl rotors on the non peroxide double-bond carbon has the lowest value, 5.26 cal mol K. ... 

To produce polymer wood, wood is degassed and then loaded according to wood type with 35%-95% monomer. The monomer is then converted by polycondensation or addition polymerization to polymer. For polycondensation, monomers that do not eliminate volatile components during polyreaction are, of course, preferred. Ring-shaped monomers as well as monomers with carbon-carbon double bonds can be polymerized. In the latter case, polymerization can be induced by 7-rays, peroxides, redox systems, etc. Not all monomers, however, are suitable for the preparation of polymer wood. For example, acrylonitrile is not soluble in its own monomer. In wood, therefore, the precipitation polymerization leads to powdery deposits and not to a continuous phase. The same problem occurs with vinyl chloride, and in this case, the boiling point of the monomer is too low. Poly (vinyl acetate) has a glass transition temperature which is too low. In addition, monomers with G values (see Chapter 12) which are too low require high 7-ray doses to induce polymerization. Copolymers of styrene and acrylonitrile, poly (methyl methacrylate), and unsaturated polyesters are used commercially. 

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