A spectroscopic study of small organic peroxyl radicals (RO2) in aqueous solution

Herrmann, Hartmut; Reese, A.; Wicktor, F.; Zellner, R.

doi:10.1016/s0022-2860(96)09479-3

Cited by 9 publications

(6 citation statements)

References 4 publications

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“…Such considerations have led over the years to the development and validation of well established experimental methods such as pulse radiolysis and laser flash photolysis techniques. [13][14][15][16][17][18][19][20][21] In most cases, radical species produced using the above techniques are coupled with UV-visible time resolved spectroscopy.…”

Section: Methodsmentioning

confidence: 99%

A new approach for studying aqueous phase OH kinetics: application of Teflon waveguides

George

Rousse

Strekowski

2003

Phys. Chem. Chem. Phys.

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Bimolecular rate coefficients for the reactions of the hydroxyl radical, OH, with methanol, ethanol, tetrahydrofuran, dimethylmalonate [CH 3 in aqueous solutions have been measured using a novel experimental approach. The centrepiece of the new experimental technique reported in this work is a Teflon AF 2400 liquid core waveguide. The physical properties of the Teflon AF 2400 liquid core waveguide allow for the construction of a micro-flowtube reaction photolysis cell with an extremely low volume and a very long optical pathway. Such a reaction system allows for a very sensitive detection of chemical transients in the aqueous phase. The micro-flowtube experiments involved competition kinetics of the OH radical with the organic reactant of interest and an SCN À anion, (k OH+SCN À ¼ 1.29 Â 10 10 M À1 s À1 ). 1 The (SCN) À 2 anion was detected using UV-visible spectroscopy following a medium pressure mercury lamp photolysis (l ! 366 nm) of H 2 O/H 2 O 2 /reactant/ KSCN mixtures. All experiments were carried out at room temperature. Measured rate coefficients for the reaction of the OH radical with methanol, ethanol, tetrahydrofuran, dimethylmalonate, dimethylsuccinate, dimethylcarbonate and diethylcarbonate are (units are 10 8 M À1 s À1 ):22, k OH+diethylcarbonate ¼ 7.9 AE 3.2. Uncertainties in the above expressions are AE2s and represent precision only. The reported rate coefficients for the reactions of OH with ethanol, methanol and THF agree very well with the currently recommended values. To date, there is no kinetic data reported in the literature for the OH radical reaction with dimethylmalonate, dimethylsuccinate, dimethylcarbonate and diethylcarbonate. The reaction mechanism is briefly discussed as a function of bond energies.

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Section: Methodsmentioning

confidence: 99%

A new approach for studying aqueous phase OH kinetics: application of Teflon waveguides

George

Rousse

Strekowski

2003

Phys. Chem. Chem. Phys.

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“…11 Most importantly, the electrostatic repulsion caused by the permanent charge tag prevents recombination of Pyr + OO , which is a common complication in reactions involving neutral ROO . 18 2. Radical ion-molecule reactions 2.1 Product studies.…”

Section: Generation Of Pyr + Oomentioning

confidence: 99%

The role of peroxyl radicals in polyester degradation – a mass spectrometric product and kinetic study using the distonic radical ion approach

Gervasoni

Khairallah

O’Hair

et al. 2015

Phys. Chem. Chem. Phys.

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Mass spectrometric techniques were used to obtain detailed insight into the reactions of peroxyl radicals with model systems of (damaged) polyesters. Using a distonic radical ion approach, it was shown that N-methylpyridinium peroxyl radical cations, Pyr(+)OO˙, do not react with non-activated C-H bonds typically present in polyesters that resist degradation. Structural damage in the polymer, for example small amounts of alkene moieties formed during the manufacturing process, is required to enable reaction with Pyr(+)OO˙, which proceeds with high preference through addition to the π system rather than via allylic hydrogen atom abstraction (kadd/kHAT > 20 for internal alkenes). This is due to the very fast and strongly exothermic subsequent fragmentation of the peroxyl-alkene radical adduct to epoxides and highly reactive Pyr(+)O˙, which both could promote further degradation of the polymer through non-radical and radical pathways. This work provides essential experimental support that the basic autoxidation mechanism is a too simplistic model to rationalize radical mediated degradation of polymers under ambient conditions.

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“…In the past, both experimental and theoretical studies have been performed on the absorption spectra of several small alkyl peroxy radicals. Among the alkyl peroxy radicals studied are the phenyl peroxy radical, ,− the two vinyl peroxy radical isomers (C 2 H 3 O 2 ), ,, the methyl peroxy radical (CH 3 O 2 ), ,, and the hydrogen peroxy radical (HO 2 ). ,, The phenyl peroxy radical is particularly interesting in that experimental results show a gas-phase absorption in the visible region at 496.4 nm; − however, high level multiconfiguration self-consistent field (MCSCF) calculations of Krauss and Osman do not predict a visible absorption for this radical …”

Section: Introductionmentioning

confidence: 99%

Origin of Substituent Effects in the Absorption Spectra of Peroxy Radicals: Time Dependent Density Functional Theory Calculations

Weisman

Head‐Gordon

2001

J. Am. Chem. Soc.

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We investigate the assignment of electronic transitions in alkyl peroxy radicals. Past experimental work has shown that the phenyl peroxy radical exhibits a transition in the visible region; however, previous high level calculations have not reproduced this observed absorption. We use time dependent density functional theory (TDDFT) to characterize the electronic excitations of the phenyl peroxy radical as well as other hydrocarbon substituted peroxy radicals. TDDFT calculations of the phenyl peroxy radical support an excitation in the visible spectrum. Further, we investigate the nature of this visible absorption using electron attachment/detachment density diagrams of the peroxy radicals and present a qualitative picture of the origin of the visible absorption based on molecular orbital perturbations. The peroxy radical substituent is also compared against isoelectronic radical groups. The visible absorption is determined to be dependent on mixing of the alkyl and radical substituent orbitals.

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A spectroscopic study of small organic peroxyl radicals (RO2) in aqueous solution

Cited by 9 publications

References 4 publications

A new approach for studying aqueous phase OH kinetics: application of Teflon waveguides

A new approach for studying aqueous phase OH kinetics: application of Teflon waveguides

The role of peroxyl radicals in polyester degradation – a mass spectrometric product and kinetic study using the distonic radical ion approach

Origin of Substituent Effects in the Absorption Spectra of Peroxy Radicals: Time Dependent Density Functional Theory Calculations

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