Alkyl peroxy radical reactivity compounds

It was again observed that rearrangement pathways comprise a substantial portion of the oxidation routes for alkylated aromatics.Since this phenomenon is mainly due to peroxy radical reactivity rather than to identity of the parent compound, it is clear that comparable rearrangements would be factors for PAHs, as well as for nitrogen-, oxygen-, and sulfur-containing heteroaromatic rings and their alkylated derivatives. 

Reactivity ratios for all the combinations of butadiene, styrene, Tetralin, and cumene give consistent sets of reactivities for these hydrocarbons in the approximate ratios 30 14 5.5 1 at 50°C. These ratios are nearly independent of the alkyl-peroxy radical involved. Co-oxidations of Tetralin-Decalin mixtures show that steric effects can affect relative reactivities of hydrocarbons by a factor up to 2. Polar effects of similar magnitude may arise when hydrocarbons are cooxidized with other organic compounds. Many of the previously published reactivity ratios appear to be subject to considerable experimental errors. Large abnormalities in oxidation rates of hydrocarbon mixtures are expected with only a few hydrocarbons in which reaction is confined to tertiary carbon-hydrogen bonds. Several measures of relative reactivities of hydrocarbons in oxidations are compared. 

The stabilizing activity of phenols is based on scavenging of the alkyl-peroxy radicals (POO ) generated in oxidizing polymers. Participation of POO in the oxidation chain transfer is thus reduced. Reactivity of phenolics with POO results, however, in chemical transformation of the original phenolic structure (antioxidant consumption). Hence, the protection of the polymer matrix is diminished in stepwise fashion. Crossconjugated dienoide compounds, e.g. quinone methides, account... 

The reactivity of 02 - with alkyl halides in aprotic solvents occurs via nucleophilic substitution. Kinetic studies confirm that the reaction order is primary > secondary > tertiary and I > Br > Cl > F for alkyl hahdes, and that the attack by 02 - results in inversion of configuration (Sn2). Superoxide ion also reacts with CCI4, Br(CH2)2Br, CeCle, and esters in aprotic media. The reactions are via nucleophilic attack by 02 on carbon, or on chlorine with a concerted reductive displacement of chloride ion or alkoxide ion. As with all oxyanions, water suppresses the nucleophilicity of 02 (hydration energy, lOOkcalmoL ) and promotes its rapid hydrolysis and disproportionation. The reaction pathways for these compounds produce peroxy radical and peroxide ion intermediates (ROO and ROO ). 

The results presented in this study allow for the elucidation of the reaction mechanism and kinetics of the major products of alkylated aromatic compounds in the troposphere. The results show that the peroxy radical chemistry achieves the conversion of dimethylphenol to unsaturated dicarbonyls and aldehydes, thereby aiding oxidation and combustion processes that either releases large amount of energy or form reactive free radicals. 

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