Peresters hydroperoxide oxidation

CH Nj reactions, 382 COClj reactions, 383 free radical addition of hexafluoroacetone, 257 identification of oxidation products CHjNj to measure peracids as peresters, 385 extinction coefficients, 388-389/ iodometry to measure -OOH, 385 NO to measure alcohols and hydroperoxides, 386 residual, simplified carbonyl envelope which results from SF exposure, 386... 

We studied dienic elastomer films (EPDM, poly-octenamer, poly-isobutylene-co -iso-prene) which react with singlet oxygen, 02, according a "ene" reaction described elsewhere1 12. The resulting hydroperoxidized polymers can also be treated by nitric oxide and acetyl chloride but the reactions result now in the formation of nitrate and perester respectively ... 

The determination of peroxides has two goals one is to monitor peroxide concentration used as initiator and catalysts and the other is to detect formation of hazardous peroxides formed as autoxidation products in ethers, acetals, dienes, and alkylaromatic hydrocarbons. A sample is dissolved in a mixture of acetic acid and chloroform. The solution is deaerated and potassium iodide reagent is added and let to react for 1 h in darkness. The iodine formed in reaction is measured by absorbance at 470 nm and result calculated to active oxygen in the sample. The method can determine hydroperoxides, peroxides, peresters, and ketone peroxides. Oxidizing and reducing agents interfere with flic determination. 

It was shown from decomposition kinetics and by treatment with dimethyl sulfide that peroxides consist of two types a fast-decomposing one composed of peradds, and a slowly decomposing one consisting of hydroperoxides and hydro-peresters. During the induction period, the slowly decomposing hydroperoxides accumulate and the oxidation rate is controlled by the rate of decomposition, which may be finally catalyzed by metal ion residues. The autoacceleration stage is controlled by the fast-decomposing peracids [22]. 

The reactions of tertiary phosphines are frequently driven by formation of the thermo-dynamically-stable phosphoryl (P=0) bond. Deoxygenation reactions are common in phosphine chemistry many oxygen-containing compounds, for instance diacyl peroxides, peresters, alkyl hydroperoxides, ozonides, amine oxides and sulphoxides, react with phosphines ... 

The most common initiating agents used in the preparation of MIPs are azo compounds like the frequently used N-N -bis isobutyronitrile (AIBN) and 2,2 -azobis-(2,4-dimethylvaleronitrile) peroxo compounds like hydroperoxides, dialkyl peroxides, diacylperoxides and peresters oxidation-reduction systems like organic/inorganic peroxide redox couples and low valency metallic or nonmetallic compoxmds as well as photolabile compounds with the tendency to absorb light, either directly or as a result of the presence of a photosensitizer [5]. 

Colorless composites with good mechanical properties can be obtained with either -butyl perbenzoate, cumene- or -butyl hydroperoxide and ascorbic acid or ascorbyl palmitate systems (50). Mechanisms for the free radical formation are given in Fig. 4. Addition of trace amounts of transition metals in their higher oxidation state (Cu", Fe" ) to the perester component further speeds up the polymerization. On admixture with the ascorbic acid derivative the metal cation is reduced to its lower oxidation state which, because it is a potent one electron reductant and will rapidly activate the free radical decomposition of the perester, which it in turn is reoxidized to its higher oxidation state. Means for prevention of oxidation of ascorbic acid or its derivatives on prolonged storage must be developed for these formulations to be suitable for dental application. 

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