Styrene ozonide

Rates of Fragmentation. The solvent dependence was studied first (Table IV). Solutions of styrene ozonide were stored at 50°C. At various intervals, samples were quenched with ice water, and the acid formed was titrated with 0.051V KOH, using phenolphthalein indicator. While the ozonide was stable in benzene, carbon tetrachloride, and chloroform... 

Table VII. Fragmentation of Styrene Ozonide at 50°C in Different Solvents...

Rule 3 electron-attracting substituents increase, electron-donating groups decrease the reaction rates. This is shown in Table X for para-substituted styrene ozonides. The Hammett equation gives a p-value of about +0.9. 

Table X. Fragmentation of Substituted Styrene Ozonides in Methanol...

The reaction of [Cr(tpp)Cl] with styrene ozonide yields an unusual isoporphyrin complex (Scheme 4). Although the overall stoichiometry corresponds to hydration of an imine, mechanistic studies suggested nucleophilic attack by an enamine upon the oxonide. Chromium(IV) intermediates are definitely precluded/ ... 

Ozone cracking is a physicochemical phenomenon. Ozone attack on olefinic double bonds causes chain scission and the formation of decomposition products. The first step in the reaction is the formation of a relatively unstable primary ozonide, which cleaves to an aldehyde or ketone and a carbonyl. Subsequent recombination of the aldehyde and the carbonyl groups produces a second ozonide [58]. Cross-linking products may also be formed, especially with rubbers containing disubstituted carbon-carbon double bonds (e.g. butyl rubber, styrene-butadiene rubber), due to the attack of the carbonyl groups (produced by cleavage of primary ozonides) on the rubber carbon-carbon double bonds. 

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... 

Ozonolysis of styrene and ethylidenecyclohexane in the presence of [ 0]benzal-dehyde yields stable secondary ozonides incorporating 0. O NMR showed that labelled oxygen appeared as the ether oxygen, not the peroxo bridge, thus confirming the Criegee mechanism as opposed to the so-called unified concept. ... 

FIGURE 2. (a) Room-temperature O NMR spectrum of the secondary ozonide of styrene obtained after ozonolysis in pentane at —78 °C. (b) Room-temperature O NMR spectrum of the secondary ozonide of styrene obtained after ozonolysis in pentane at —78°C in the presence of 1.0 equiv. of O-labeUed benzaldehyde. Reproduced by permission of Wiley-VCH Verlag GmbH from Reference 15... 

Solid styrene was exposed at — 196°C to ozone, in an attempt to discern whether the behavior of the system is similar to that of olefinic compounds, yielding an ozonide, or to that of aromatic compounds, yielding a 7r-complex. On heating to about — 100°C, an adduct is formed that is stable until about —55 °C, when benzaldehyde and a peroxidic polymer are slowly obtained. The structure of the adduct is probably that of a POZ, based on the similarity of the IR spectrum with the ozone adduct of vinyl chloride described in the preceding paragraph . 

On stirring at room temperature ozonides of terminal alkenes (prepared in dichloromethane at — 70 °C) with a polymer-supported tertiary amine obtained from chloromethylated poly(styrene/divinylbenzene) and piperidine, followed by filtration and concentration under reduced pressure, the products (aldehydes or ketones) can be obtained easily in almost pure form in high yields <2003T493>. However, yields are low for cycloalkenes because apparently they form monomeric and polymeric ozonides. 

CM Fig. 6.7.2. Effect of acidity/basicity on decomposition of a styrene-type ozonide. (Kolsaker and Bailey 1967)... 

Clearly in the case of the stilbenes, if the above proposal mechanisms are correct, half of the aldehydes produced must have resulted from the hydrolysis of hydroperoxide intermediates. With the unsymmetrical olefins, styrene, anethole, isosafrole, estragole, and 1-dodecene, this may not be the case. If cleavage of the primary ozonide is unimolecular, then the inductive and resonance contributions of substituents Ri and R2 in X should determine the direction of cleavage. Thus, if E-i is more capa-... 

Peroxide catalysts and ozonides are generally employed as initiators for cross-linking unsaturated polyesters. The formation of active radicals that can initiate the hardening copolymerization reaction may be begun also by ferrocene and some of its derivatives (acetyl ferrocene, benzyl ferrocene, etc.) [73]. Note that styrene-containing unsaturated polyesters will polymerize at room temperature without a... 

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