The Bimolecular Self-reactions of Secondary Peroxy Radicals. Product Studies

Lindsay, D. G.; Howard, J. A.; Horswill, E. C.; Iton, Lennox E.; Ingold, K. U.; Cobbley, T.; Ll, A.

doi:10.1139/v73-131

Cited by 51 publications

(27 citation statements)

References 7 publications

(15 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although the elimination of molecular hydrogen has been observed in the decomposition of peroxides (9), the simultaneous formation of molecular hydrogen and oxygen from the tetroxide appears unlikely. The occurrence of the termination reaction 3c is supported by the detection by colorimetric analysis ( I I ) of hydrogen peroxide in the samples.…”

Section: [Traduit Par Le Journal]mentioning

confidence: 98%

Product Studies of the Mutual Termination Reactions of sec-Alkylperoxy Radicals: Evidence for Non-Cyclic Termination

Bennett¹,

Summers²

1974

Can. J. Chem.

View full text Add to dashboard Cite

The yields of alcohol and ketone from the mutual termination reaction of sec-butyl-, sec-hexyl-, cyclopentyl-, and cycloheptylpesoxy radica!~ have been measured over the temperature range from -125 to + l o 0 "C. The ratio of alcohol/ketone departs markedly from the value of unity predicted by the Russell mechanism, being greater (ca. 2.5) at +I00 " C and considerably less (ca. 0.1) at -125 "C. -125 "C. [Traduit par le journal]Can. J . Chem., 52, 1377 (1974) The mutual termination reactions of primary or secondary alkylperoxy radicals are generally assumed to proceed through a cyclic transition state (i.e., the Russell mechanism) (1-3) where the overall termination rate constant, 2k, = 2k, k , k,/k-, k-,. On this basis it has been concluded from thermochemical calculations that the overall activation energy, E,, should be negative (4). However, recent measurements (5) by electron spin resonance spectroscopy of 2k, for several see-alkylperoxy radicals have shown that E, is positive (2-4 kcal mol-') and that the Arrhenius plots are not linear a t low temperatures.Product studies (6-8), mainly at ambient temperature, have shown that comparable yields of alcohol and ketone are formed as predicted by the Russell mechanism (eq. 1). However, detailed studies (9) have shown recently that at ambient temperatures considerable fractions of 1-ethoxyethylperoxy radicals and 1,2-diphenylethylperoxy radicals d o not terminate by the Russell mechanism but form free alkoxy radicals by a route (eq. 2a) comparable to that postulated for the termination of tert-alkylperoxy radicals. In view of the anomalous temperature dependence of the rate constants (5) we have now made product studies over a comparable temperature range (-125 to + 100 "C) for the see-alkylperoxy radicals from butane, hexane, cyclopentane, and cycloheptane. The peroxy radicals were formed by the photolysis of an oxygenated solution of di-tert-butyl peroxide (0.25 to 4%) in the appropriate hydrocarbon (5). This method formed specific see-alkylperoxy radicals from butane, cyclopentane, and cycloheptane but gave a mixture of the 2-and 3-hexylperoxy radicals from hexane. The products were identified and their concentrations measured by gas-liquid chromatography.Detailed product analyses were made for the cyclopentylperoxy radical and appropriate control experiments were carried out. The yields of Can. J. Chem. Downloaded from www.nrcresearchpress.com by 52.183.12.225 on 04/29/19For personal use only.

show abstract

Section: [Traduit Par Le Journal]mentioning

confidence: 98%

Product Studies of the Mutual Termination Reactions of sec-Alkylperoxy Radicals: Evidence for Non-Cyclic Termination

Bennett¹,

Summers²

1974

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…The bimolecular reaction of pentamethylbenzylperoxyl radicals may also produce pentamethylbenzyl alcohol, pentamethylbenzaldehyde, and oxygen, which is the termination step in the radical chain reaction in Scheme 2. 50, 51 Since the aldehyde has hardly been detected, the termination step is negligible as compared with the efficient radical chain process in Scheme 2.…”

Section: A R T I C L E Smentioning

confidence: 99%

Scandium Ion-Promoted Photoinduced Electron Transfer from Electron Donors to Acridine and Pyrene. Essential Role of Scandium Ion in Photocatalytic Oxygenation of Hexamethylbenzene

et al. 2004

View full text Add to dashboard Cite

Photoinduced electron transfer from a variety of electron donors including alkylbenzenes to the singlet excited state of acridine and pyrene is accelerated significantly by the presence of scandium triflate [Sc(OTf)(3)] in acetonitrile, whereas no photoinduced electron transfer from alkylbenzenes to the singlet excited state of acridine or pyrene takes place in the absence of Sc(OTf)(3). The rate constants of the Sc(OTf)(3)-promoted photoinduced electron-transfer reactions (k(et)) of acridine to afford the complex between acridine radical anion and Sc(OTf)(3) remain constant under the conditions such that all the acridine molecules form the complex with Sc(OTf)(3). In contrast to the case of acridine, the k(et) value of the Sc(OTf)(3)-promoted photoinduced electron transfer of pyrene increases with an increase in concentration of Sc(OTf)(3) to exhibit first-order dependence on [Sc(OTf)(3)] at low concentrations, changing to second-order dependence at high concentrations. The first-order and second-order dependence of k(et) on [Sc(OTf)(3)] is ascribed to the 1:1 and 1:2 complexes formation between pyrene radical anion and Sc(OTf)(3). The positive shifts of the one-electron redox potentials for the couple between the singlet excited state and the ground-state radical anion of acridine and pyrene in the presence of Sc(OTf)(3) as compared to those in the absence of Sc(OTf)(3) have been determined by adapting the free energy relationship for the photoinduced electron-transfer reactions. The Sc(OTf)(3)-promoted photoinduced electron transfer from hexamethylbenzene to the singlet excited state of acridine or pyrene leads to efficient oxygenation of hexamethylbenzene to produce pentamethylbenzyl alcohol which is further oxygenated under prolonged photoirradiation of an O(2)-saturated acetonitrile solution of hexamethylbenzene in the presence of acridine or pyrene which acts as a photocatalyst together with Sc(OTf)(3). The photocatalytic oxygenation mechanism has been proposed based on the studies on the quantum yields, the fluorescence quenching, and direct detection of the reaction intermediates by ESR and laser flash photolysis.

show abstract

“…Because of the presence of the solvent cage in the condensed phase, primary and secondary peroxy radicals can undergo further reactions to form two ketones and hydrogen peroxide (R1); an alcohol, a ketone, and oxygen (R2); or two alkoxy radicals and oxygen (R3). Importantly, because of the presence of the radical cage, the formation of "free" alkoxy radicals, which are thought to be responsible for fragmentation in aerosol, has a much lower branching ratio (~5-10%) 23 in the condensed phase compared with the branching ratio for the gas phase formation of alkoxy radicals (~60-90%). 13 This mechanism also implies that the "Russell mechanism" and the "BennettSummers mechanism" are not actually separate mechanisms, but rather the product branching ratio of the RO2 + RO2 reaction depends on molecular structure and temperature.…”

Section: Introductionmentioning

confidence: 99%

Stochastic methods for aerosol chemistry: a compact molecular description of functionalization and fragmentation in the heterogeneous oxidation of squalane aerosol by OH radicals

Wiegel

Wilson

Hinsberg

et al. 2015

Phys. Chem. Chem. Phys.

115

View full text Add to dashboard Cite

show abstract

The Bimolecular Self-reactions of Secondary Peroxy Radicals. Product Studies

Cited by 51 publications

References 7 publications

Product Studies of the Mutual Termination Reactions of sec-Alkylperoxy Radicals: Evidence for Non-Cyclic Termination

Product Studies of the Mutual Termination Reactions of sec-Alkylperoxy Radicals: Evidence for Non-Cyclic Termination

Scandium Ion-Promoted Photoinduced Electron Transfer from Electron Donors to Acridine and Pyrene. Essential Role of Scandium Ion in Photocatalytic Oxygenation of Hexamethylbenzene

Stochastic methods for aerosol chemistry: a compact molecular description of functionalization and fragmentation in the heterogeneous oxidation of squalane aerosol by OH radicals

Contact Info

Product

Resources

About