Isoprene hydroperoxides

This extensive data set showed good agreement with a Master Chemical Mechanism for isoprene oxidation. In addition, one of the predictions of the mechanism is that at low NOx levels, like those seen in Surinam, isoprene hydroperoxides (six isomers, e.g. HOCH2C(OOH)(CH3)CH=CH2) will accumulate. It was noted that correlations between isoprene and other VOCs (different times of day and altitude) were greatest with MlOl ", which could be indicative of isoprene hydroperoxides. This result is an example where PTR-MS analysis can detect previously unmeasured VOCs, although as mentioned above, verification of the identity of unknown positive ions requires complementary methods (e.g. GC-MS). 

FIGURE 28.6 Concentrations of isoprene (m/z 69), meth-ylvinyl ketone and methacrolein (m/z 71), and possibly isoprene hydroperoxides (m/z 101) as a function of height (full line) and time of day. Reprinted with permission from Reference [62], Copyright 2000 Elsevier. 

Dimethyl peroxide Diethyl peroxide Di-t-butyl-di-peroxyphthalate Difuroyl peroxide Dibenzoyl peroxide Dimeric ethylidene peroxide Dimeric acetone peroxide Dimeric cyclohexanone peroxide Diozonide of phorone Dimethyl ketone peroxide Ethyl hydroperoxide Ethylene ozonide Hydroxymethyl methyl peroxide Hydroxymethyl hydroperoxide 1-Hydroxyethyl ethyl peroxide 1 -Hydroperoxy-1 -acetoxycyclodecan-6-one Isopropyl percarbonate Isopropyl hydroperoxide Methyl ethyl ketone peroxide Methyl hydroperoxide Methyl ethyl peroxide Monoperoxy succinic acid Nonanoyl peroxide (75% hydrocarbon solution) 1-Naphthoyl peroxide Oxalic acid ester of t-butyl hydroperoxide Ozonide of maleic anhydride Phenylhydrazone hydroperoxide Polymeric butadiene peroxide Polymeric isoprene peroxide Polymeric dimethylbutadiene peroxide Polymeric peroxides of methacrylic acid esters and styrene... 

An interesting redox system for grafting, containing cumene hydroperoxide and Fe + ions, has been developed by Simionescu et al. U. They grafted acrylonitrile and isoprene to rayon fibers at low temperatures (20 to A0°C) and long reaction times (up to... 

The catalytic or initiated reaction involves heating the poly(diene) in an aromatic solvent to temperatures between 120-150 °C in the presence of free radical initiators such as peroxides, hydroperoxides and azo compounds. The ensuing reaction involves addition of maleic anhydride to a polymeric radical which was formed by abstraction of an allylic hydrogen by initiator radicals. Four modes of addition are possible leading to partial structures such as (175)-(178) illustrated with poly(isoprene). It can readily be seen that some crosslinking is an inherent problem because of structures (177) and (178). The amount of gel formed, however, is found to be largely dependent on the initiator employed and can be minimized, especially with hydroperoxide initiators. 

Stereoselective epoxidation,2 0=Mo(TPP)OCH3, 0=Mo(TPP)Cl, and cis-02Mo(TPP) catalyze the epoxidation of cyclohexene with /-butyl hydroperoxide with formation of the insoluble [OMo(TPP)]20. These molybdenum complexes are comparable to Mo(CO)6, but exhibit a longer induction period. The epoxidation of cis- and tranr-2-hexene catalyzed with O—Mo(TPP)Cl is highly stereospeciflc the cis- and /ra s-2-epoxides are formed in 97% and 99% yield, respectively. The cis-2-hexene oxide is formed 3.5 times faster than the trans-isomer, an indication of efficient steric control because of the bulky ligand. Another difference is observed in epoxidation of isoprene with Mo(CO)6 and O—Mo(TPP)OCH3 (equation I). 

Emulsion polymerization of styrene in the persulfate and hydroperoxide-polyamine systems, and isoprene in the hydroperoxide-polyamine system (32)... 

This high reactivity towards the important atmospheric photo-oxidants, probably valid also for similar isoprene oxidation products like unsaturated hydroxy carbonyls, hydroxy nitrates or hydroxy hydroperoxides, is an indication that these reactions need more consideration in laboratory experiments as well as photooxidation models. 

Ozonolysis in water was carried out by mixing a solution of the alkene in water (water/acetonitrile in the case of isoprene and the pinenes) with an aqueous solution of ozone The hydroperoxide yields are in Table 3. The only significant products were 1-HAHPs [4]. 

Either direction of cleavage of the primary ozonide from a-pinene would produce a carbonyl oxide with ten carbon atoms. Fragmentation of this intermediate might well lead to a number of hydroperoxides we could detect, but only MHP was observed from gas-phase ozonolysis. As in the case of isoprene, neutralisation of the sample from aqueous ozonolysis before analysis indicates that significant amounts of HAHPs are formed in water. These are still under investigation. 

Isoprene polymers, both of low molecular weight such as squalene, and of high molecular weight such as natural rubber and gutta percha also differ from mono-olefins in that intramolecular reactions can occur because of the multiple unsaturation and the short distances between the double bonds. For such materials it has been shown that a diperoxide-hydroperoxide structure is formed which Holland and Hughes (1949) proposed as ... 

Reaction Scheme 7.7 Pathways of the products found in the reaction of isoprene and NO3 for (A) C4-carbonyl, (B) Cs-hydroxy carbonyl, (C) hydroxy nitrate, (D) nitroxy aldehyde, and (E) nitroxy hydroperoxide (Perring et al. 2009)... 

Improvements in available methodology for the oxidation of alkenes to oxirans have been described. Glycidol can be obtained in 90% yield by heating allyl alcohol with cumene hydroperoxide at 110 °C using vanadium oxychloride as catalyst. Oxidation of isoprene with peroxyformic acid gave an 80% crude yield of the vinyl oxiran, which was treated with lithium chloride and cupric chloride to give the useful synthon (15), a key intermediate in the synthesis of vitamin A from j3-ionone. This modified synthesis employs a hitherto unprecedented oxidative chlorination of a vinyl oxiran (Scheme 4). Previously, the best known method for the oxidation... 

Peroxidation of cw-poly(isoprene) leads in part to the formation of vicinal hydroperoxides as shown in Scheme 1. This process has been known for many years [5-7] but its full significance for rubber biodegradation has been recognised only recently. The low molar mass peroxidation products are rapidly biassimilated under environmental conditions. In addition, however, carbon dioxide and water, the normal end points of biodegradation, are also formed in significant quantities during abiotic oxidation and... 

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